Set Environment label in alerta to cluster_name

Change-Id: If7ea4e8bf99eeb37bcfb3fb7a3511bf75a885a3b
Related-PROD: PROD-21806
diff --git a/docker/swarm/stack/monitoring/alerta.yml b/docker/swarm/stack/monitoring/alerta.yml
index 858eb38..5e99286 100644
--- a/docker/swarm/stack/monitoring/alerta.yml
+++ b/docker/swarm/stack/monitoring/alerta.yml
@@ -29,3 +29,4 @@
                 ADMIN_USERS: ${_param:alerta_admin_username}
                 ADMIN_PASSWORD: ${_param:alerta_admin_password}
                 MONGO_URI: ${_param:alerta_mongodb_uri}
+                PLUGINS: ""