CI: Last attempt at getting tag trigger syntax right

.circleci/config.yml

@@ -120,8 +120,11 @@ workflows:
               only: master
       - docker-push-tag:
           filters:
+            # Only build for tag, not for branch
             tags:
               only: /^v.*/
+            branches:
+              ignore: /.*/
   rebuild-images:
     triggers:
       - schedule: