WL#4189 mtr.pl v2

 - Fix faulty regex used for filtering out suspicious warnings, causing
   warnings/errors from previous tests to be reported

mysql-test/mysql-test-run.pl

@@ -3388,7 +3388,7 @@ sub extract_warning_lines ($) {
   my @lines;
   while ( my $line = <$Ferr> )
   {
-    if ( $line =~ /"^CURRENT_TEST:"/ )
+    if ( $line =~ /^CURRENT_TEST:/ )
     {
       # Throw away lines from previous tests
       @lines = ();