we actually need to get a filedescriptor to the backend.

This also makes it evident for vcl_pass{}, vcl_pipe{} and vcl_miss{}
if the client sent a Host: header or not.  Previously these functions
saw the default Host: header.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@3118 d4fa192b-c00b-0410-8231-f00ffab90ce4