Do not wait for lock file cleanup on Windows

As signals are currently not handled by named on Windows, instances
terminated using signals are not able to perform a clean shutdown, which
involves e.g. removing the lock file.  Thus, waiting for a given
instance's lock file to be removed beforing assuming it is shut down
is pointless on Windows, so do not even attempt it.

(cherry picked from commit 761ba451)

bin/tests/system/stop.pl

@@ -141,6 +141,8 @@ exit($errors);
 sub server_lock_file {
 	my ( $server ) = @_;
 
+	return if (defined($ENV{'CYGWIN'}));
+
 	return $testdir . "/" . $server . "/named.lock" if ($server =~ /^ns/);
 	return if ($server =~ /^ans/);
 	return $testdir . "/" . $server . "/lwresd.lock" if ($server =~ /^lwresd/);