Migrate to testrepository.

Needed to move some directory creation around to be contained within the
testcase, but with parallel testing, we shave 48 seconds off the run
time and go from around 60s to around 11. We're also now compatible with
future subunit-based fast-fail semantics when we grow them.

Change-Id: I6c7148c29d1edb5d9469a8c2afe4b31b2b340009
Reviewed-on: https://review.openstack.org/33352
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins