"nginx only uses HTTP/1.0 when it proxies requests to a back end server"
No more:
http://www.quora.com/Why-doesnt-Nginx-talk-HTTP-1-1-to-upstr...
http://nginx.org/en/docs/http/ngx_http_upstream_module.html#...
http://mailman.nginx.org/pipermail/nginx/2011-August/028324....