Re-enable test_can_merge unit test

Expose the ability to refresh a change in zuul/connection/gerrit.py
too, which is needed for our unit testing.

Change-Id: Iefd09d9b8deef563299e0f209d95e25b61aa4c1e
Signed-off-by: Paul Belanger <pabelanger@redhat.com>
3 files changed