enter LOITER mode

def set_mode_loiter(self):
        '''enter LOITER mode'''
        if self.mavlink10():
            self.mav.command_long_send(self.target_system, self.target_component,
                                       mavlink.MAV_CMD_NAV_LOITER_UNLIM, 0, 0, 0, 0, 0, 0, 0, 0)
        else:
            MAV_ACTION_LOITER = 27
            self.mav.action_send(self.target_system, self.target_component, MAV_ACTION_LOITER)