Fix mysql-test-run.pl to work after d6d5c168cf

option values now have to be edited in-place,
instead of replacing an option with another one
that has the same name but a new value.

mysql-test/lib/My/ConfigFactory.pm

@@ -372,7 +372,7 @@ sub resolve_at_variable {
   }
   $res .= $after;
 
-  $config->insert($group->name(), $option->name(), $res)
+  $option->{value}= $res;
 }