fix: ensure local connection is properly closed in CheckLocalConn method

[HynoR]

What this PR does / why we need it?

#11409

本地稳定复现，不是ws ssh的问题，而是这个不起眼的函数的问题

Summary of your change

修复 checkconnection 检查链接后，不对建立链接做关闭的问题

这个函数会创建一个 ssh 链接，返回一个实例

这里用_ 忽略了返回，但是依然存在建立的链接，没有调用close方法去关闭 FD，导致 fd 泄露。

@ssongliu

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