see if an unsigned packet should be allowed

def allow_unsigned(self, mav, msgId):
        '''see if an unsigned packet should be allowed'''
        if self.allow is None:
            self.allow = {
                mavutil.mavlink.MAVLINK_MSG_ID_RADIO : True,
                mavutil.mavlink.MAVLINK_MSG_ID_RADIO_STATUS : True
                }
        if msgId in self.allow:
            return True
        if self.settings.allow_unsigned:
            return True
        return False