Fix Nginx proxy for Nagios UI port

The port 8001 is used internaly by collectors/aggregator to push statuses.

https://github.com/Mirantis/mk-lab-salt-model/pull/160
diff --git a/nginx/server/proxy/nagios_web.yml b/nginx/server/proxy/nagios_web.yml
index d1a54f8..8b57929 100644
--- a/nginx/server/proxy/nagios_web.yml
+++ b/nginx/server/proxy/nagios_web.yml
@@ -8,8 +8,8 @@
           type: nginx_proxy
           name: nagios
           proxy:
-            host: mon01
-            port: 8001
+            host: ${_param:stacklight_monitor_address}
+            port: 80
             protocol: http
           host:
             name: ${_param:cluster_public_host}