Currently, Xtrabackup is used for database backups. However, Xtrabackup
is not compatible with MariaDB 10.3. This change switches to use
mariabackup [1], which is available in the mariadb image.

The documented full and incremental restore procedures have been
modified to use mariabackup, following [2] and [3].

[1] https://mariadb.com/kb/en/library/mariabackup-overview/
[2] https://mariadb.com/kb/en/library/full-backup-and-restore-with-mariabackup/
[3] https://mariadb.com/kb/en/library/incremental-backup-and-restore-with-mariabackup/

Change-Id: Id52b9b1f7b013277e401b1f6b8aed34473d2b2c4
Closes-Bug: #1843043
Depends-On: https://review.opendev.org/691290

Since we use the release name as the default tag to publish images
to Dockerhub, we should use this by default.

This change also removes support for the magic value "auto".

Change-Id: I5610cc7729e9311709147ba5532199a033dfd156
Closes-Bug: #1843518

We copy-paste the same play into various playbooks to detect
openstack_release. This change factors that code into a separate
playbook that is imported.

Change-Id: I5fea005642b960080bf5e43455618dc24766c386

blueprint database-backup-recovery

Introduce a new option, mariadb_backup, which takes a backup of all
databases hosted in MariaDB.

Backups are performed using XtraBackup, the output of which is saved to
a dedicated Docker volume on the target host (which defaults to the
first node in the MariaDB cluster).

It supports either full (the default) or incremental backups.

Change-Id: Ied224c0d19b8734aa72092aaddd530155999dbc3

Change-Id: Icb9b097299011cc09f3012bbee9629a5457c920c
Closes-Bug: #1681316

Change-Id: I44c2668a8ebb6dd3201a6eb4e47284871380e6d7

This playbook only matters for multinode since AIO can recover from
power outage without additional configuration.

DocImpact
Implements: blueprint mariadb-lights-out
Change-Id: I903c3bcd069af39814bcabcef37684b1f043391f