Add HTTPS proxy for Prometheus and Alertmanager

Change-Id: I57a04c716290891cfc0fe32a23a09d6c2843b837
Closes-bug: PROD-20150
diff --git a/docker/swarm/stack/monitoring/alertmanager.yml b/docker/swarm/stack/monitoring/alertmanager.yml
index 1f15be5..877984a 100644
--- a/docker/swarm/stack/monitoring/alertmanager.yml
+++ b/docker/swarm/stack/monitoring/alertmanager.yml
@@ -3,7 +3,7 @@
 parameters:
   _param:
     alertmanager_external_url: ${_param:cluster_public_host}
-    alertmanager_external_proto: http
+    alertmanager_external_proto: https
   docker:
     client:
       stack: