Adding x-forwarded-port/scheme header in the request should be well taken into account

Currently the VirtualHostHelper takes only the x-forwarded-scheme into account and take it always even if the local flag is activated in the getServerUrl() method.

This leads to 404 error when following links because of the UrlPolicyService using it internally.

See http://answers.nuxeo.com/questions/9813/https-reverse-proxy-now-fails-with-http-404-with-upgrade-to-595-is-it-my-fault-or-bug-in-latest-release?page=1#9826 for a sample buggy situation