gsutil: use depot_tools.gsutil_py_path instead of path['depot_tools']

scripts/slave/recipe_modules/archive/example.expected/cf_archiving_svn_no_git.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport json, os, sys\nif os.path.exists(sys.argv[1]) and os.path.isdir(sys.argv[1]):\n  with open(sys.argv[2], 'w') as f:\n    json.dump(os.listdir(sys.argv[1]), f)\n",
       "[SLAVE_BUILD]/src/out/Release",
       "/path/to/tmp/json"
     ],
     "name": "listdir build_dir",
@@ skipping 19 matching lines @@
       "chrome-asan-linux-release-refs_heads_B1-123456",
       "[\"chrome\"]",
       "[SLAVE_BUILD]/src/out/Release"
     ],
     "name": "zipping"
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[DEPOT_TOOLS]/gsutil.py",
+      "RECIPE_PACKAGE_REPO[depot_tools]/gsutil.py",
       "--",
       "-h",
       "x-goog-meta-Cr-Commit-Position:refs/heads/B1@{#123456}",
       "-h",
       "x-goog-meta-Cr-Commit-Position-Number:123456",
       "cp",
       "[TMP_BASE]/chrome_staging_tmp_1/chrome-asan-linux-release-refs_heads_B1-123456.zip",
       "gs://chromium/linux-release/chrome-asan-linux-release-refs_heads_B1-123456.zip"
     ],
     "name": "gsutil upload",
@@ skipping 16 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@os.remove(sys.argv[1])@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]