Use zaqar-tempest-plugin for zaqar jobs
Use zaqar-tempest-plugin for zaqar jobs

* https://review.openstack.org/#/c/504893/ and https://review.openstack.org/504899
  enables zaqar tempest plugin from a seperate repo.
* It would be good to consume this plugin in CI jobs.

Change-Id: I5be26216d1ee04306a56850674bfc30b84192092

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