stop the service

def on_stop(self):
        """
        stop the service
        """
        LOGGER.debug("natsd.Service.on_stop")
        self.is_started = False
        try:
            next(self.nc.unsubscribe(self.serviceQS))
        except StopIteration as e:
            pass
        try:
            next(self.nc.close())
        except StopIteration as e:
            pass
        try:
            for task in asyncio.Task.all_tasks(self.loop):
                task.cancel()
            self.loop.stop()
            while self.loop.is_running():
                time.sleep(1)
            self.loop.close()
        except Exception as e:
            LOGGER.debug("natsd.Service.on_stop - Exception aio clean up : "
                         + traceback.format_exc())