Use registry:2 image mirrored to quay.io

In our container job roles and tests we sometimes need to set up a
registry. In those caes we've typically been using registry:2 from
docker.io. Docker has put in place some pretty strict rate limits so
we've mirrored the image to quay.io as an alternative source location.
Fetch the image from that location.

Change-Id: Idccaa350bd2951d5b56314ea4f19bdcb9c13d1a1

test-playbooks/registry/roles/run-test-intermediate-registry/tasks/main.yaml

@@ -47,4 +47,4 @@
     --env REGISTRY_AUTH_HTPASSWD_REALM="Registry Realm"
     --volume="/var/registry/certs:/certs"
     --volume="/var/registry/auth:/auth"
-    docker.io/library/registry:2
+    quay.io/opendevmirror/registry:2

util-tasks/run-docker-registry.yaml

@@ -47,6 +47,6 @@
     -e "REGISTRY_AUTH=htpasswd" \
     -e "REGISTRY_AUTH_HTPASSWD_REALM=Registry Realm" \
     -e REGISTRY_AUTH_HTPASSWD_PATH=/auth/htpasswd \
-    registry:2
+    quay.io/opendevmirror/registry:2
   args:
     chdir: "{{ registry_tempdir.path }}"