Use constraints for coverage job
Use constraints for coverage job

OpenStack CI supports now constraints in the coverage job - as a first
job to check that recent changes for zuul-cloner work correctly.

Use constraints for cover environment. If this works successfully, the
other environments can be updated in followups.

Change-Id: I6069bee0a89d38f6a3ec57418e7bda9850dc6f64
(cherry picked from commit 1a95ac48b757a7d3050339fe72837f71f0351d74)

cyx1231st/nova,cyx1231st/nova,NeCTAR-RC/nova,NeCTAR-RC/nova