Fix a vulnerability when NettyClient sent data encountered an exception

[gosonzhang]

This bug fix mainly addresses the following 3 situations:

1. NettyClient may have been closed when sending;
2. An exception is thrown during the sending process, and the request may have been removed;
3. During the sending process, the exception is thrown，the request still exists, but the exception causes are different；the sending logic with the callback function needs to clear the timeout event to handle the exception.

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   此错误修复主要解决以下3种情况：

4. NettyClient发送时可能已经关闭； 2.在发送过程中引发异常，并且该请求可能已被删除； 3.在发送过程中，抛出异常，请求仍然存在，但异常原因不同；带有回调函数的发送逻辑需要清除超时事件以处理异常。

[lizhiboo]

+1