当浏览器不小心请求代理的端口时，代理会无限代理这个请求

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#### Which platform are you running AnyProxy

Linux
#### The version of the AnyProxy

4.1.2

#### Your expected behavior of AnyProxy

代理应该过滤掉对代理自身的请求
#### The actual behavior of AnyProxy

比如说我的代理的端口是8080，地址是anyproxy.example.com，不小心在浏览器地址栏输入anyproxy.example.com:8080的时候，在anyproxy的web面板会看到非常多对anyproxy.example.com:8080的请求，返回500
#### The log of the error

Start by reproducing the reported loop on Linux with AnyProxy 4.1.2: configure port 8080, then request anyproxy.example.com:8080 from a browser. Trace how AnyProxy handles requests addressed to its own proxy endpoint; done means the self-request is filtered instead of repeatedly proxied and returning many 500 responses.

Written by the indexing model from the issue text.