Enable Style/EmptyLinesAround Module/Class Body cop

## What does this MR do?
Enable a new rubocop cops as discussed here: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1877/diffs#note_13021078

## Are there points in the code the reviewer needs to double check?
May be a good idea to send a message to people to prevent `master` red because of the new cop.

## Why was this MR needed?
We want to improve code style and not waste endbosses time checking style manually

## What are the relevant issue numbers?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5692