Revert of ensure_goma for goma canary

scripts/slave/recipe_modules/goma/resources/ensure_goma.py

Index: scripts/slave/recipe_modules/goma/resources/ensure_goma.py
diff --git a/scripts/slave/recipe_modules/goma/resources/ensure_goma.py b/scripts/slave/recipe_modules/goma/resources/ensure_goma.py
index a2679d34f073e1811bc9baf71ef2b1096fe7347b..b65956b2b1e5d33e7948d2939db7a49d2f47ea4e 100755
--- a/scripts/slave/recipe_modules/goma/resources/ensure_goma.py
+++ b/scripts/slave/recipe_modules/goma/resources/ensure_goma.py
@@ -30,7 +30,6 @@
   parser = argparse.ArgumentParser()
   parser.add_argument('--target-dir', required=True)
   parser.add_argument('--download-from-google-storage-path', required=True)
-  parser.add_argument('--canary', action='store_true')
 
   args = parser.parse_args()
 
@@ -47,11 +46,8 @@
     subprocess.check_call(['git', 'clone', config['repo'], client_dir])
 
   subprocess.check_call(['git', 'fetch'], cwd=client_dir)
-  rev = config['revision']
-  if arg.canary:
-    rev = 'refs/heads/master'
   subprocess.check_call(
-      ['git', 'reset', '--hard', rev], cwd=client_dir)
+      ['git', 'reset', '--hard', config['revision']], cwd=client_dir)
 
   subprocess.check_call([sys.executable,
                          args.download_from_google_storage_path,