When using multiples server names in `server_name`, the NGINX variable
`$server_name` will always point only to the first entry. `$host`
variable, instead, point to the selected host from the user (HTTP
request or Host: header).
Because we are using openwrt and we would like to mantain LUCI running
on it's interface we can't bind on 0.0.0.0. or 127.0.0.1 hence we must
listen on a specific ip. This will set the public ip from the group
vars to be the one where we listen