Don't process/queue children not matched

It seems like children that are unmatched are
still submitted onto the queue (and then they
don't do anything) when we can just avoid that
processing in the first place by just not
submitting them in the first place.

Change-Id: I5d576faab25b3a47b395b9f627b131370d31e191

kolla/image/build.py

@@ -266,6 +266,8 @@ class BuildTask(DockerTask):
             ])
         if self.image.children and self.success:
             for image in self.image.children:
+                if image.status == STATUS_UNMATCHED:
+                    continue
                 followups.append(BuildTask(self.conf, image, self.push_queue))
         return followups