Add real_ip setting to nginx example.

Merged username-removed-379455 requested to merge 3kami3/gitlab-ce:real_ip into master

What does this MR do?

Changes the bundled NGINX configuration files to support real IP address.
reference:
https://docs.gitlab.com/omnibus/settings/nginx.html#configuring-gitlab-trusted_proxies-and-the-nginx-real_ip-module

Are there points in the code the reviewer needs to double check?

Nothing.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

none.