Update mq queue mirror directive to match vhost

Updates the definition for queue mirroring to use the same vhost as the
queue itself is defined to be.

Change-Id: Ibb631d7adb237fa17c5e853a9e9e35297a525782

charts/shipyard/values.yaml

@@ -354,7 +354,7 @@ conf:
   rabbitmq:
     # adding rmq policy to mirror messages from celery queues
     policies:
-      - vhost: "/"
+      - vhost: "airflow"
         name: "ha_celery"
         definition:
           ha-mode: "all"