varnish using as a proxy interfering with get requests

[varnish list]

Hello

I'm attempting to use varnish in a somewhat unusual manner, but with fairly
good reason I think.

browser -> varnish server :80 -> apache proxy (localhost:3128) -> any site

the idea being to use varnish to fire off statd timing info to get metrics
on operations against an number of systems, some we run, some out sourced,
in a standard manner

issue is varnish 4.1.3, but I've tried other 4's, interferes with the users
request

I'm comparing the request using tshark and varnishlog

proxy request can look like

GET http://website.dom/url
I see that hit varnish from the browser

what apache gets is
GET /url

I can't figure out what is stripping the http://website.dom. My default.vcl
is practically empty

vcl 4.0;
import std;
import statsd;
import timers;

backend default {
    .host = "127.0.0.1";
    .port = "3128";
}

sub vcl_recv {
    return (pass);
}

sub vcl_backend_response {
}

sub vcl_deliver {
    if (req.url ~ "/REST/UI/Content/CheckOut") {
       statsd.incr("website.checkout");
    }
}

sub vcl_init {
        statsd.server( "statdcollector.dom", "8125" );
        statsd.prefix( "proxy.test." );
}

varnish 3.0.5 didn't do this, but its statd and timing support isn't great
and old hat, so I'm none too interesting in sticking with 3

Any clues where I find and disable this interference?

Thanks

Neil
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