mariadb-upgrade has had its own upgrade version file in the datadir,
called mysql_upgrade_info in <= 10.11 and mariadb_upgrade_info there
after.
The mariadb-install-db creates this file, and also the mariadb-upgrade
executable creates this file also.
This removes the need to maintain the .version info though this is used
as a last check of the upgrade.
Signed-off-by: Daniel Black <daniel@mariadb.org>