VTC for gunzip in an included response, with the junk after data error.

Before the bugfix for Varnish #3109
(d235b3c90a631ef39fdf0a8103e44ebfb0ddbacb), the gunzip VDP went into
an infinite loop for such a case.

src/tests/junk-after-gunzip.vtc

+varnishtest "VDP gunzip for an include, when there is junk after gzip"
+
+server s1 {
+	rxreq
+	txresp -body {<Before esi>
+<esi:include src="/junk.html"/>
+After esi
+}
+} -start
+
+server s2 {
+	rxreq
+	expect req.url == "/junk.html"
+	txresp -hdr "content-encoding: gzip" -nolen
+	# cf Varnish r03109.vtc
+	sendhex "1f 8b 08 00 f5 8a b9 5d 02 03 0b 4f 4d 51 30 36"
+	sendhex "50 f0 4f 2e 51 30 34 b1 32 30 b7 32 30 54 70 76"
+	sendhex "0d 51 30 32 30 b4 e4 02 00 fa 76 79 ba 1d 00 00"
+	sendhex "00 62 61 64 0a"
+} -start
+
+varnish v1 -vcl+backend {
+	import ${vmod_pesi};
+
+	sub vcl_backend_fetch {
+		if (bereq.url == "/") {
+			set bereq.backend = s1;
+		}
+		else {
+			set bereq.backend = s2;
+		}
+	}
+
+	sub vcl_backend_response {
+		if (bereq.url == "/") {
+			set beresp.do_esi = true;
+		}
+		else {
+			set beresp.filters = "";
+		}
+	}
+
+	sub vcl_deliver {
+		set resp.filters = "pesi";
+		if (req.esi_level == 1) {
+			set resp.filters = "pesi gunzip";
+		}
+	}
+} -start
+
+client c1 {
+	txreq
+	rxresp
+	expect resp.status == 200
+	expect resp.bodylen == 24
+	expect resp.body == {<Before esi>
+
+After esi
+}
+} -run
+
+logexpect l1 -v v1 -d 1 -q "vxid == 1001" {
+	expect * 1001	Gzip {^G.un.zip error: 1 .junk after VGZ_END.$}
+} -start
+
+## HTTP/2
+
+# TBD