MDEV-24177 && MDEV-24178

- MDEV-24177: main.sp2 test fails: Result length mismatch
- MDEV-24178: main.upgrade_MDEV-19650 test fails: Result length mismatch

Reviewed by: serg@mariadb.com

mysql-test/mysql-test-run.pl

@@ -3365,6 +3365,7 @@ sub mysql_install_db {
   mtr_add_arg($args, "--tmpdir=%s", "$opt_vardir/tmp/");
   mtr_add_arg($args, "--core-file");
   mtr_add_arg($args, "--console");
+  mtr_add_arg($args, "--character-set-server=latin1");
 
   if ( $opt_debug )
   {