mtr bug: files outside of both the suite dir and the overlay dir, were

treated as coming from the overlay.
  
(example: archive suite, test_sql_discovery overlay, mysql-test/include/have_archive.inc)

mysql-test/lib/mtr_cases.pm

@@ -968,6 +968,8 @@ sub get_tags_from_file($$) {
   } elsif ($over and $file =~ m@^$pdir/(.*)$@) {
     $suffix = $1;
     @prefix = map { "$_/" } $sdir, $pdir;
+  } else {
+    $over = 0; # file neither in $sdir nor in $pdir
   }
 
   while (my $line= <$F>)