Update haproxy to forward the original IP address.

Trac requires this for the IP throttling plugin to work correctly. Without this, everything is throttled because it only sees the proxy's IP.

I tested this by modifying the production haproxy.cfg and running:

cd /root/mediagoblin-compose /root/docker-compose-venv/bin/docker-compose up --build --force-recreate --no-deps haproxy