check if we should send new data to the APM

def check_apm_out(self):
        '''check if we should send new data to the APM'''
        now = time.time()
        if now - self.last_apm_send_time < 0.02:
            return
        self.last_apm_send_time = now
        if self.hil_state_msg is not None:
            self.master.mav.send(self.hil_state_msg)