do a compass/motor interference calibration

def cmd_compassmot(self, args):
        '''do a compass/motor interference calibration'''
        mav = self.master
        print("compassmot starting")
        mav.mav.command_long_send(mav.target_system, mav.target_component,
                                  mavutil.mavlink.MAV_CMD_PREFLIGHT_CALIBRATION, 0,
                                  0, 0, 0, 0, 0, 1, 0)
        self.compassmot_running = True
        self.empty_input_count = self.mpstate.empty_input_count