* Robben, Mandzukic on target * Bayern defender Dante scores own goal * Guardiola makes winning league start (Updates with quotes, details) MUNICH, Aug 9 (Reuters) - Treble winners Bayern Munich launched their Bundesliga title defence with a commanding 3-1 victory over Borussia Moenchengladbach on Friday to mark a winning German league debut for new coach Pep Guardiola. ... More...