Add stable/zed jobs on master gate

As zed is released, we should add its job on master
gate to keep branchless tempest plugins compatible
to stable branch.

Ref: Tempest plugins guide for stable branch testing:
- https://docs.openstack.org/tempest/latest/stable_branch_testing_policy.html

Change-Id: Ia20cec2a500943a7f954c34614102c4d17a01c34
1 file changed