It used to be the case that GitLab created symlinks for each repository
to one copy of the Git hooks, so these ran when required. This changed
to set the hooks dynamically on Gitaly when invoking Git.
The side effect is that we didn't need all these symlinks anymore, which
Gitaly doesn't create anymore either. Now that means that the tests in
GitLab-Rails should test for it either.
Related: https://gitlab.com/gitlab-org/gitaly/issues/1392#note_175619926
Cleanup code, and refactor tests that still use Rugged. After this, there should
be no Rugged code that access the instance's repositories on non-test
environments. There is still some rugged code for other tasks like the
repository import task, but since it doesn't access any repository storage path
it can stay.
