new test: proxy protocol and x-forward-proto

[NotBad4U]

• set up an application with:
  • one backend
  • a sozu in tcp mode with send_proxy=true
  • a sozu behind the send_proxy with expect_proxy=true and in http mode
• the backend send back the forwarded headers present in the request.
• the client sends a request (no keep-alive)
• we check that we got a response from the backend with the forwarded headers expected. The headers should be:
  • X-Forwarded-Proto: http
  • X-Forwarded-For: <identifier>
  • X-Forwarded-Port: <port>
  • Forwarded: proto=http;for=<identifier>;by=<host>
• check in the access log of sozu-tcp|http the client ip and the port is present