Set 'request_access_enabled' false by default

What does this MR do?

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21992

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

Maybe 😄

Why was this MR needed?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21992

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • [ ] Added for this feature/bug
  • [ ] All builds are passing
• [ ] Conform by the merge request performance guides
• [ ] Conform by the style guides
• [ ] Branch has no merge conflicts with master (if it does - rebase it please)
• [ ] Squashed related commits together

What are the relevant issue numbers?