Some unit tests were missing from the GitLab API v4 change. We had the
beginnings of a function for checking repositories against the v4 API,
but it never actually performed any checks (and was missing a necessary
part of the payload to make the checks happen).

This fills in the missing logic, and adds a utility function for setting
the API version for a test so spies don't need to be repeated in several
places.

Testing Done:
Unit tests pass.

Reviewed at https://reviews.reviewboard.org/r/9789/