Update Stacklight os-contrail models

Change-Id: Ife02f91f1179dbbf8ec72c26435844415dded9be
diff --git a/classes/cluster/sl_os_contrail/stacklight/proxy.yml b/classes/cluster/sl_os_contrail/stacklight/proxy.yml
index 9933070..8b71bcb 100755
--- a/classes/cluster/sl_os_contrail/stacklight/proxy.yml
+++ b/classes/cluster/sl_os_contrail/stacklight/proxy.yml
@@ -9,6 +9,7 @@
 parameters:
   _param:
     nginx_proxy_grafana_port: 15013
+    cluster_public_host: ${_param:prometheus_control_address}
     nginx_proxy_ssl:
       enabled: true
       authority: ${_param:salt_minion_ca_authority}