Enable monitoring support for the Grafana stack

Change-Id: I571a99ed4339df212b539475e33f6c790e1cae04
diff --git a/docker/swarm/stack/dashboard.yml b/docker/swarm/stack/dashboard.yml
index 2ee123b..62a3e14 100644
--- a/docker/swarm/stack/dashboard.yml
+++ b/docker/swarm/stack/dashboard.yml
@@ -1,3 +1,5 @@
+classes:
+- service.grafana.support
 parameters:
   _param:
     docker_grafana_replicas: 1