Add '--adb-keys-file $HOME/.android/*.pub' to all bot provision_devices calls.

scripts/slave/recipe_modules/chromium_android/example.expected/gerrit_try_builder_basic.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 322 matching lines @@
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "[SLAVE_BUILD]/src/build/android/provision_devices.py",
       "-t",
       "Release",
-      "--skip-wipe"
+      "--skip-wipe",
+      "--adb-key-files /usr/local/google/home/navabi/.android/*.pub"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "provision_devices"
   },
   {
     "cmd": [
       "python",
       "-u",
@@ skipping 113 matching lines @@
       "[SLAVE_BUILD]/src/build/android/asan_symbolize.py",
       "-l",
       "[SLAVE_BUILD]/src/out/Release/full_log"
     ],
     "env": {
       "PATH": "[SLAVE_BUILD]/src/third_party/android_tools/sdk/platform-tools:[SLAVE_BUILD]/src/build/android:%(PATH)s"
     },
     "name": "stack_tool_for_asan"
   }
 ]