[autotest] Use _get_label_action() for acts_on()

BUG=chromium:707999
TEST=Run unit tests

Change-Id: I69344a64b010113662e4b6e768ce7e790a17d3ff
Reviewed-on: https://chromium-review.googlesource.com/446880
Commit-Ready: Allen Li <ayatane@chromium.org>
Tested-by: Allen Li <ayatane@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/server/cros/provision.py b/server/cros/provision.py
index 2039abc..9762785 100644
--- a/server/cros/provision.py
+++ b/server/cros/provision.py
@@ -167,7 +167,8 @@
         @returns: True if there exists a test to run for this label.
 
         """
-        return label.split(':')[0] in cls._actions
+        action = _get_label_action(label)
+        return action.name in cls._actions
 
 
     @classmethod