Add HTTPS proxy for Prometheus and Alertmanager

Change-Id: I57a04c716290891cfc0fe32a23a09d6c2843b837
Closes-bug: PROD-20150
diff --git a/nginx/server/proxy/monitoring/prometheus_server.yml b/nginx/server/proxy/monitoring/prometheus_server.yml
index 76ff56a..d9eb261 100644
--- a/nginx/server/proxy/monitoring/prometheus_server.yml
+++ b/nginx/server/proxy/monitoring/prometheus_server.yml
@@ -14,3 +14,5 @@
           host:
             name: ${_param:cluster_public_host}
             port: 15010
+            protocol: https
+          ssl: ${_param:nginx_proxy_ssl}