At the moment it's not possible to apply different versions of
services to the different groups due to playbook vars having
prescedence over group_vars. However, it can be quite important
to such use cases, for example for phased rollouts of newer versions.
This will also reduce amount of unnecessary variables that are included
for each host, since only required git details will be loaded.
Closes-Bug: #2007296
Depends-On: https://review.opendev.org/c/openstack/openstack-ansible-os_rally/+/881954
Change-Id: Icaa3a958926d9f9aa6cb649bd9f3da9449dd7490
9fca8555df