brpc服务端下电一个节点，brpc客户端并没有重新选择链接，持续上报EPOLLOUT错误，连接超时。

**Describe the bug**
出现问题的场景：brpc服务端下电一个节点，brpc客户端并没有重新选择链接，持续上报EPOLLOUT错误，连接超时。

待brpc服务端重新上电后，客户端连接恢复。

**To Reproduce**
目前只遇到过一次

**Expected behavior**
期望brpc重新发起socket连接，并且连接成功，而不是一直等待原节点。

**Versions**
OS:ubuntu
Compiler:g++
brpc:1.9
protobuf:

**Additional context/screenshots**

No source file or test is identified. Start by reproducing the client behavior while shutting down one server node and inspect how EPOLLOUT errors and socket reconnection are handled; done means the client retries, selects a healthy node, and does not wait for the powered-off node to return.

Written by the indexing model from the issue text.