Use pause-buildset-registry role

opendev/system-config needed this so we pulled it into a role.
Might as well use it here too.

Depends-On: https://review.opendev.org/709256
Change-Id: Ie5f038f8c0d45fb20ced34c5e133fe08476362a1

playbooks/docker-image/run.yaml

@@ -7,10 +7,5 @@
 # are running it, pause the job so that child jobs will automatically
 # use it.
 - hosts: localhost
-  tasks:
-    - name: Pause the job
-      when: buildset_registry is not defined
-      zuul_return:
-        data:
-          zuul:
-            pause: true
+  roles:
+    - pause-buildset-registry