re-dev possible memory leak

I use a simple code to only receive rocketmq normal messages and orderly messages. Return true when the message is received.
The sender sends a packet of ordinary data and a packet of real-time data in 100ms.
The following is the memory information graph from 2021-06-15 to 2021-06-28

[rocketmqrecvtest.txt](https://github.com/apache/rocketmq-client-cpp/files/6723828/rocketmqrecvtest.txt)

從附加的 rocketmqrecvtest.txt 和記憶體圖表開始，接著重現回報的 receiver 工作負載，並觀察記憶體使用量隨時間的變化。當確認並修正疑似的記憶體洩漏，且有證據表明在相同的一般與即時訊息流量下記憶體維持穩定時，該 issue 即完成。

由索引模型根據 Issue 內容生成。