This patch was generated by replacing:
`proxy_set_header Host $http_host` ->
`proxy_set_header Host $host`
Script:
find . -type f -exec sed -i 's|proxy_set_header Host \$http_host|proxy_set_header Host \$host|g' {} \;
Fixes test error:
```
>> Problem: [host_spoofing] The proxied Host header may be spoofed.
Description: In most cases "$host" variable are more appropriate, just use it.
Additional info: https://github.com/yandex/gixy/blob/master/docs/en/plugins/hostspoofing.md
```
`proxy_set_header Host $host` is indeed the recommended default proxy header setting.
