Add ovn-sb-db-relay

Following stackhpc/kolla#376

Author: mnasiadka

ansible/inventory/group_vars/all/kolla

@@ -111,6 +111,7 @@ kolla_container_images:
   - ovn-nb-db-server
   - ovn-northd
   - ovn-sb-db-server
+  - ovn-sb-db-relay
   - placement-api
   - placement-base
   - prometheus-alertmanager