Started implementing Host header propagation for asynchronous invocations

Add Host field to the queue.Request struct and copy it from Host field
of the HTTP request when converting HTTP request to queue.Request in
MakeQueuedProxy function.

Signed-off-by: Dmitri Rubinstein <dmitri.rubinstein@googlemail.com>

gateway/handlers/queueproxy.go

@@ -50,6 +50,7 @@ func MakeQueuedProxy(metrics metrics.MetricOptions, wildcard bool, canQueueReque
 			Method:      r.Method,
 			QueryString: r.URL.RawQuery,
 			Header:      r.Header,
+			Host:        r.Host,
 			CallbackURL: callbackURL,
 		}