switch proxy_protocol option -> proxy_protocol_port

[pjenvey]

ELB health checks are incompatible with its proxy protocol option (it won't use the proxy protocol for the health check):

https://forums.aws.amazon.com/thread.jspa?messageID=738720

To workaround this we need to expose both a proxy protocol enabled port and another port without the proxy protocol for the status check. To keep it simple we'll just make a proxy_protocol_port option to specify an alternate port, exposing everything twice.