Make freezer-api-ubuntu as voting job again
Make freezer-api-ubuntu as voting job again

freezer-api-ubuntu job has been made n-v in legacy
job migration work.
- https://review.openstack.org/#/c/642607/

Not issue has been fixed and it is working fine
- https://review.openstack.org/#/c/643213/3

Let's reenable it as voting and running on gate pipeline also.

Change-Id: Idd8ee0c8d2540d40a855e10581f9f350f1adb069

openstack/freezer-api,openstack/freezer-api,openstack/freezer-api,openstack/freezer-api