chromium_tests: remove unnecessary path component from cache checkout path

scripts/slave/recipes/chromium.expected/kitchen_path_config.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_",
       "511"
     ],
     "name": "makedirs checkout path",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@import sys, os@@@",
       "@@@STEP_LOG_LINE@python.inline@path = sys.argv[1]@@@",
       "@@@STEP_LOG_LINE@python.inline@mode = int(sys.argv[2])@@@",
       "@@@STEP_LOG_LINE@python.inline@if not os.path.isdir(path):@@@",
       "@@@STEP_LOG_LINE@python.inline@  if os.path.exists(path):@@@",
@@ skipping 22 matching lines @@
       "{\"src\": \"got_revision\", \"src/buildtools\": \"got_buildtools_revision\", \"src/native_client\": \"got_nacl_revision\", \"src/third_party/angle\": \"got_angle_revision\", \"src/third_party/webrtc\": \"got_webrtc_revision\", \"src/tools/swarming_client\": \"got_swarming_client_revision\", \"src/v8\": \"got_v8_revision\"}",
       "--git-cache-dir",
       "[GIT_CACHE]",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@HEAD",
       "--force",
       "--output_manifest"
     ],
-    "cwd": "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_",
+    "cwd": "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_",
     "env": {
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"fixed_revisions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"src\": \"HEAD\"@@@",
@@ skipping 117 matching lines @@
       "@@@STEP_LOG_LINE@json.output@    }@@@",
       "@@@STEP_LOG_LINE@json.output@  ]@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/tools/swarming_client/swarming.py",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/tools/swarming_client/swarming.py",
       "--version"
     ],
     "name": "swarming.py --version",
     "stdout": "/path/to/tmp/",
     "~followup_annotations": [
       "@@@STEP_TEXT@0.4.10@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "runhooks"
     ],
-    "cwd": "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src",
+    "cwd": "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "archive_gpu_tests=1 component=static_library ffmpeg_branding=Chrome gomadir='[CACHE]/cipd/goma' proprietary_codecs=1 target_arch=x64 test_isolation_mode=prepare use_goma=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/testing/scripts/get_compile_targets.py",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/testing/scripts/get_compile_targets.py",
       "--output",
       "/path/to/tmp/json",
       "--",
       "--build-config-fs",
       "Release",
       "--paths",
-      "{\"checkout\": \"[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src\", \"runit.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py\", \"runtest.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/slave/runtest.py\"}",
+      "{\"checkout\": \"[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src\", \"runit.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py\", \"runtest.py\": \"RECIPE_PACKAGE_REPO[build]/scripts/slave/runtest.py\"}",
       "--properties",
       "{\"buildername\": \"Linux Kitchen (kitchen_run)\", \"buildnumber\": \"77457\", \"mastername\": \"chromium.fyi\", \"slavename\": \"build1-a1\", \"target_platform\": \"linux\"}"
     ],
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/testing/buildbot/chromium.fyi.json",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/testing/buildbot/chromium.fyi.json",
       "/path/to/tmp/json"
     ],
     "name": "read test spec (chromium.fyi.json)",
     "~followup_annotations": [
-      "@@@STEP_TEXT@path: [BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/testing/buildbot/chromium.fyi.json@@@",
+      "@@@STEP_TEXT@path: [BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/testing/buildbot/chromium.fyi.json@@@",
       "@@@STEP_LOG_LINE@json.output@{}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py",
       "--show-path",
       "python",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/cleanup_temp.py"
     ],
     "name": "cleanup_temp"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/tools/mb/mb.py",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/tools/mb/mb.py",
       "gen",
       "-m",
       "chromium.fyi",
       "-b",
       "Linux Kitchen (kitchen_run)",
       "--config-file",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src/tools/mb/mb_config.pyl",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src/tools/mb/mb_config.pyl",
       "--goma-dir",
       "[CACHE]/cipd/goma",
       "//out/Release"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "generate_build_files"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py",
       "--show-path",
       "python",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/compile.py",
       "--gsutil-py-path",
       "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "--ninja-path",
       "RECIPE_PACKAGE_REPO[depot_tools]/ninja",
       "--target",
       "Release",
       "--src-dir",
-      "[BUILDER_CACHE]/checkouts/Linux_Kitchen__kitchen_run_/src",
+      "[BUILDER_CACHE]/Linux_Kitchen__kitchen_run_/src",
       "--goma-cache-dir",
       "[GOMA_CACHE]",
       "--goma-deps-cache-dir",
       "[GOMA_DEPS_CACHE]",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
@@ skipping 13 matching lines @@
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]