Make some perl scripts usable with git bisect run

For that they need to return between 0 and 124 on error, while die returns
255, causing bisect-run to abort.
diff --git a/tests/scripts/test-ref-configs.pl b/tests/scripts/test-ref-configs.pl
index c3d1426..020bafc 100755
--- a/tests/scripts/test-ref-configs.pl
+++ b/tests/scripts/test-ref-configs.pl
@@ -43,7 +43,8 @@
 system( "cp $config_h $config_h.bak" ) and die;
 sub abort {
     system( "mv $config_h.bak $config_h" ) and warn "$config_h not restored\n";
-    die $_[0];
+    warn $_[0];
+    exit 1;
 }
 
 while( my ($conf, $args) = each %configs ) {