[4.1] 7c593da Cover also the case where backend sends nothing with chunked encoding

[Poul-Henning Kamp]

commit 7c593da13ba58096bfb472f6b0b0c7e0718cda35
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Wed Sep 16 08:59:16 2015 +0000

    Cover also the case where backend sends nothing with chunked encoding

diff --git a/bin/varnishtest/tests/r01783.vtc b/bin/varnishtest/tests/r01783.vtc
index c44b77f..f938a62 100644
--- a/bin/varnishtest/tests/r01783.vtc
+++ b/bin/varnishtest/tests/r01783.vtc
@@ -4,7 +4,8 @@ server s1 {
 	rxreq
 	txresp -hdr "foo: 1"
 	rxreq
-	txresp -hdr "foo: 2"
+	txresp -nolen -hdr "foo: 2" -hdr "Transfer-Encoding: chunked"
+	chunkedlen 0
 } -start
 
 varnish v1 -vcl+backend {} -start