Merge branch 'lm-update-ha-app-server-config' into 'master'

HA Application Servers should have nginx running on them.

See merge request gitlab-org/gitlab-ee!5427

doc/administration/high_availability/gitlab.md

@@ -57,6 +57,7 @@ for each GitLab application server in your environment.
 
     # Disable components that will not be on the GitLab application server
     roles ['application_role']
+    nginx['enable'] = true
 
     # PostgreSQL connection details
     gitlab_rails['db_adapter'] = 'postgresql'