package/mariadb: do not pass --user=mysql to mysql_install_db

package/mariadb: do not pass --user=mysql to mysql_install_db

We currently install the default database by passing --user=mysql to the
install script. With the upcoming bump to the 10.4 series, this does not
work as intended. An error occurs because of missing PAM modules. We work
around this now by creating the default db as root and calling chown to
change the files to user mysql.

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