This change allows the following use cases:
1. Using an already-configured MariaDB / MySQL server / Cluster
2. Using already-created DB users, without requiring root DB access.
Update: added external mariadb precheck
Change-Id: I78b0d178306d7c5293b0bf53e445f19f18b4b824
Implements: blueprint external-mariadb-support.
Closes-Bug: #1603121
through the database_address has beed defined in groups_vars/all.yml, we should
better use it, this way, if we want to use external database, we just need to
redefined in all.yml
refer to https://github.com/openstack/kolla-ansible/blob/master/ansible/group_vars/all.yml#L83
Co-Authored-By: chenqiaomin <chen.qiaomin@99cloud.net>
Change-Id: Ie559301451954e16347ceaabf02f594c5c5cbe56
