package/mariadb: fix permissions of data dir when using systemd

package/mariadb: fix permissions of data dir when using systemd

mysql_install_db is currently called in the systemd unit without
--user=mysql that the sysv script uses. This will generate the initial
database files with root permissions. However, mysqld runs as user mysql
so this will cause problems. We fix this by calling chown instead of
passing the user parameter because an upcoming version bump will fail when
ran this way.

Signed-off-by: Ryan Coe <bluemrp9@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>