adb: move known devices file under cache so it works with remote_run

scripts/slave/recipe_modules/chromium_android/example.expected/webview_cts_expected_failure.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport os, sys\n\nbuild_path = sys.argv[1]\nif os.path.exists(build_path):\n  for (path, dir, files) in os.walk(build_path):\n    for cur_file in files:\n      if cur_file.endswith('index.lock'):\n        path_to_file = os.path.join(path, cur_file)\n        print 'deleting %s' % path_to_file\n        os.remove(path_to_file)\n",
       "[SLAVE_BUILD]"
     ],
     "name": "cleanup index.lock",
     "~followup_annotations": [
@@ skipping 259 matching lines @@
   },
   {
     "cmd": [],
     "name": "fix_device_file_format"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "[BUILD]/site_config/.known_devices",
+      "[CACHE]/known_android_devices",
       "/path/to/tmp/"
     ],
     "name": "fix_device_file_format.read_device_file",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_TEXT@file format is compatible@@@"
     ]
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/src/build/android/buildbot/bb_device_status_check.py",
       "--adb-path",
       "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools/adb",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
       "--json-output",
       "/path/to/tmp/json",
       "--known-devices-file",
-      "[BUILD]/site_config/.known_devices"
+      "[CACHE]/known_android_devices"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "device_status_check",
     "~followup_annotations": [
       "@@@STEP_TEXT@Online devices: 1@@@",
       "@@@STEP_LOG_LINE@json.output@[@@@",
       "@@@STEP_LOG_LINE@json.output@  {@@@",
@@ skipping 110 matching lines @@
   },
   {
     "cmd": [],
     "name": "fix_device_file_format (2)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "[BUILD]/site_config/.known_devices",
+      "[CACHE]/known_android_devices",
       "/path/to/tmp/"
     ],
     "name": "fix_device_file_format.read_device_file (2)",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_TEXT@file format is compatible@@@"
     ]
   },
   {
     "cmd": [
       "[SLAVE_BUILD]/src/build/android/buildbot/bb_device_status_check.py",
       "--adb-path",
       "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools/adb",
       "--blacklist-file",
       "[SLAVE_BUILD]/src/out/bad_devices.json",
       "--json-output",
       "/path/to/tmp/json",
       "--known-devices-file",
-      "[BUILD]/site_config/.known_devices"
+      "[CACHE]/known_android_devices"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "device_status_check (2)",
     "~followup_annotations": [
       "@@@STEP_TEXT@Online devices: 1@@@",
       "@@@STEP_LOG_LINE@json.output@[@@@",
       "@@@STEP_LOG_LINE@json.output@  {@@@",
@@ skipping 360 matching lines @@
       "@@@STEP_TEXT@<br/>unexpected failures:<br/>android.webkit.cts.WebSettingsTest#testUserAgentString_default<br/>@@@",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "Unexpected Test Failures.",
     "status_code": 1
   }
 ]