message: fix password update in maxscale.sql
diff: CREATE USER IF NOT EXISTS 'maxscale'@'%';
  -UPDATE mysql.user SET PASSWORD=PASSWORD("maxscale") WHERE user="maxscale";
  +ALTER USER maxscale IDENTIFIED VIA mysql_native_password USING PASSWORD("maxscale");
  GRANT SELECT ON mysql.user to 'maxscale'@'%';
  GRANT SELECT ON mysql.db TO 'maxscale'@'%';
  