Also fixes:
MDEV-21487: Implement option for mysql_upgrade that allows root@localhost to be replaced
MDEV-21486: Implement option for mysql_install_db that allows root@localhost to be replaced

Add user mariadb.sys to be definer of user view
(and has right on underlying table global_priv for
required operation over global_priv
(SELECT,UPDATE,DELETE))

Also changed definer of gis functions in case of creation,
but they work with any definer so upgrade script do not try
to push this change.