Proxy Protocol strings have dest and src reversed

[bneradt]

I noticed that when we configure ATS to send Proxy Protocol via proxy.config.http.proxy_protocol_out, our Proxy Protocol strings have src and dest descriptions reversed:

trafficserver/proxy/http/HttpSM.cc

Line 132 in 3dcf2a8

info = ProxyProtocol{pp_version, local.family(), local, vc_in->get_remote_endpoint()};

We should pass vc_in->get_remote_endpoint() (which is the client's src address) before local (which is the client's dest address).

I have an internal Yahoo patch I'm working on for this with an AuTest that I plan to opensource soon.