Update the build worker to remove all tags from expired images.

workers/dockerfilebuild.py

@@ -352,17 +352,23 @@ class DockerfileBuildContext(object):
           # We can forget about this particular tag if it was indeed one of our renamed tags
           self.private_repo_tags.discard(tag)
 
-        verify_removed.add(image_id)
+          try:
+            self._build_cl.remove_image(tag)
+          except APIError:
+            # Sometimes an upstream image removed this one
+            pass
+
         try:
           self._build_cl.remove_image(image_id)
         except APIError:
           # Sometimes an upstream image removed this one
           pass
+        verify_removed.add(image_id)
 
     # Verify that our images were actually removed
     for image in self._build_cl.images():
       if image['Id'] in verify_removed:
-        raise RuntimeError('Image was not removed: %s' % image['Id'])
+        logger.warning('Image was not removed: %s' % image['Id'])
 
   def __cleanup(self):
     # Iterate all of the images and rename the ones that aren't public. This should preserve