如果只是host，如http://host
带：用代理的内容替换掉匹配的路径
不带：拼接上匹配的路径
2：如果是子路径，如http://host/func
带和不带：用代理的内容替换掉匹配的路径
假设有原始请求http://xxx/say/hello，示例如下（注意标红处）
| 场景 | location | proxy_pass | 请求地址 |
|---|---|---|---|
| host/ | /say | http://host/ | http://host//hello |
| host/ | /say/ | http://host/ | http://host/hello |
| host | /say | http://host | http://host/say/hello |
| host | /say/ | http://host | http://host/say/hello |
| host/sub/ | /say | http://host/speak/ | http://host/speak//hello |
| host/sub/ | /say/ | http://host/speak/ | http://host/speak/hello |
| host/sub | /say | http://host/speak | http://host/speak/hello |
| host/sub | /say/ | http://host/speak | http://host/speakhello |
