Adds initial support for Mariadb with Galera replication in Ansible
using the CONFIG_EXTERNAL methods.
Additionally, this refactors some of the Galera config script to allow
for reuse by CONFIG_EXTERNAL.
Partially Implements: blueprint ansible-service
Change-Id: I566fea0376ecca39fc8a5167f9ff9ff434ea7b7e
efbfd7912b