[trove] CI job migration to Bionic for stable/stein

Hi team, I've fixed the problems that blocked the job migration for the master, now according to the community requirement, we also need to finish the migration for stable/stein. I've already backported the needed patches, please review or reply directly to this email if you have any concerns. https://review.openstack.org/#/c/649744/ https://review.openstack.org/#/c/649745/ --- Cheers, Lingxian Kong Catalyst Cloud