Adjust buildset registry container name

If we want to run a second registry on a different port, we'll need
a different name for the docker container.

Change-Id: I887d9015c0d21e6d7f95379e6fa7fb4211e58d3d

roles/run-buildset-registry/tasks/main.yaml

@@ -42,7 +42,7 @@
     certificate: "{{ certificate.content | b64decode }}"
 - name: Start the buildset registry
   docker_container:
-    name: buildset_registry
+    name: "{{ (buildset_registry_port == 5000) | ternary('buildset_registry', 'buildset_registry_' + buildset_registry_port|string) }}"
     image: zuul/zuul-registry:latest
     state: started
     restart_policy: always