Clean up driverfixes branch jobs
Clean up driverfixes branch jobs

There have been a few jobs added that need to be skipped
for the driverfixes/* branches. Also cleaning up some
stable/mitaka references as that is now EOL.

Change-Id: Ic0db267dc725737dd55900d7fe9917a373494300

openstack-infra/project-config,openstack-infra/project-config