Implement http.CloseNotifier interface for gzipResponseWriter

This seems to have been an oversight since all of the response writers
are supposed to implement this interface, but the gzipResponseWriter
didn't implement this interface for some reason.

services/httpd/handler.go

@@ -756,6 +756,10 @@ func (w gzipResponseWriter) Flush() {
 	w.Writer.(*gzip.Writer).Flush()
 }
 
+func (w gzipResponseWriter) CloseNotify() <-chan bool {
+	return w.ResponseWriter.(http.CloseNotifier).CloseNotify()
+}
+
 // determines if the client can accept compressed responses, and encodes accordingly
 func gzipFilter(inner http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {