更新队列线程

def _watchdog(self):
        """
        更新队列线程
        """
        sid = self._playingsong['sid']
        while 1:

            # 本次播放里去重
            while 1:
                song = douban.get_song(sid)
                if not song:
                    continue
                sid = song['sid']
                if sid not in self.hash_sid:
                    break

            self._playlist.put(song)
            if not self._playingsong:
                self._playlist.get(False)