[RFE] Kolla-Ansible should stop and deploy Galera safely

[Pierre Riteau]

The Galera documentation explains how it is possible to restart a cluster safely by making sure the most advanced node is started first: http://galeracluster.com/documentation-webpages/restartingcluster.html

We should make sure `kolla-ansible stop` stops running Galera containers in a specific order so that the most advanced node is identified.

Then `kolla-ansible deploy` could be tuned to restart Galera using the most advanced node first, which would hopefully remove the requirement of running the mariadb_recovery command. At the very least it would help identifying which node to use as `mariadb_recover_inventory_name`.