Useful for upgrade etc., which is preferablly done serially.
Example usage: tools/kolla-ansible deploy OR tools/kolla-ansible upgrade
Closes-Bug: #1576708
DocImpact
Change-Id: I34b2e16f8ce53e472a4682a4738c4ac0f5abf00c
After introduction of pull action and turing every main.yml into
{{action}}.yml we lost ability to perform upgrade
Change-Id: Ie9fa2cd083b061033abc733fba53d54f9c55e393
Fixes-Bug: #1538210