Stop the monitoring thread of the plugin.

        The super-class will send the stop signal on the monitor-IP queue,
        which prompts the loop to stop.

def stop(self):
        """
        Stop the monitoring thread of the plugin.

        The super-class will send the stop signal on the monitor-IP queue,
        which prompts the loop to stop.

        """
        super(Icmpecho, self).stop()
        self.monitor_thread.join()
        logging.info("ICMPecho health monitor plugin: Stopped")