Disarm the vehicle.

        If wait is True, wait for disarm operation to complete before
        returning.  If timeout is nonzero, raise a TimeouTerror if the
        vehicle has not disarmed after timeout seconds.

def disarm(self, wait=True, timeout=None):
        '''Disarm the vehicle.

        If wait is True, wait for disarm operation to complete before
        returning.  If timeout is nonzero, raise a TimeouTerror if the
        vehicle has not disarmed after timeout seconds.
        '''
        self.armed = False

        if wait:
            self.wait_for(lambda: not self.armed, timeout=timeout,
                          errmsg='failed to disarm vehicle')