mtr: fix the check where a combination is pre-selected

if all options from a combination from the combinations file are already
present in the server's list of options, then don't try to run tests
in other combinations from this file.

old behavior was: if at least one option from a combination is
already present in the list...

mysql-test/lib/My/Options.pm

@@ -140,24 +140,16 @@ sub diff {
 }
 
 
-sub is_set {
-  my ($opts, $set_opts)= @_;
+sub is_subset {
+  my ($set, $subset)= @_;
+  my %cache = map { _split_option($_) } @$set;
 
-  foreach my $opt (@$opts){
-
-    my ($opt_name1, $value1)= _split_option($opt);
-
-    foreach my $set_opt (@$set_opts){
-      my ($opt_name2, $value2)= _split_option($set_opt);
-
-      if ($opt_name1 eq $opt_name2 and $value1 eq $value2){
-	# Option already set
-	return 1;
-      }
-    }
+  for (@$subset){
+    my ($name, $value)= _split_option($_);
+    return 0 unless exists $cache{$name} and $cache{$name} eq $value;
   }
 
-  return 0;
+  return 1;
 }
 
 

mysql-test/lib/mtr_cases.pm

@@ -623,8 +623,10 @@ sub make_combinations($$@)
   {
     # Skip all other combinations if the values they change
     # are already fixed in master_opt or slave_opt
-    if (My::Options::is_set($test->{master_opt}, $comb->{comb_opt}) &&
-        My::Options::is_set($test->{slave_opt}, $comb->{comb_opt}) ){
+    # (empty combinations are not considered a subset of anything)
+    if (@{$comb->{comb_opt}} &&
+        My::Options::is_subset($test->{master_opt}, $comb->{comb_opt}) &&
+        My::Options::is_subset($test->{slave_opt}, $comb->{comb_opt}) ){
 
       $test_combs->{$comb->{name}} = 2;