Namespace license checks for repository mirrors

Related to https://gitlab.com/gitlab-org/gitlab-ee/issues/2335

Mirror external repositories (EES / Bronze)

1. Do not display Pull from Remote Repository or Push to a Remote Repository under repository settings page.

2. How to handle for future cases where this has already been set?

Experts: me, @brodock, and @tiagonbotelho

mentioned in issue #2335 (closed)

assigned to @to1ne

mentioned in merge request !2328 (merged)

closed via merge request !2328 (merged)

mentioned in commit 55f5f936

https://na34.salesforce.com/0016100000KvaIg?srPos=1&srKp=001

Note from the customer re: feature requirements:

We currently have this open functionality request to restrict repository mirroring by group:

https://gitlab.com/gitlab-org/gitlab-ee/issues/1144

We see that it's still in progress. As we cannot currently restrict repository mirroring by group, we need to completely disable repository mirroring, as we have an internal requirement that all mirrored repositories must go through a single team for creation. What configuration changes do we need to make to completely disable repository mirroring on GitLab EE?