Fix tempest compatibility

Now Tempest tests are not running with our Tempest jobs.
Tempest commit https://review.openstack.org/#/c/123589/ has changed Tempest
tox jobs, so we need to use another tox job to be able to run our Tempest
tests.

Change-Id: I166637916347e03010781e4ca97fd901a6181b48
Merge "Fix tempest compatibility"