Add H/2 stream data head of line blocking test case

This is the test case that fails if these changes aren't in tree. Note the
commented out rxwinup commands that are necessary for the proper fail mode
when run without the varnishtest window update changes.

bin/varnishtest/tests/t02017.vtc

+varnishtest "H/2 stream data head of line blocking"
+
+barrier b1 cond 2
+barrier b2 cond 2
+barrier b3 cond 2
+barrier b4 cond 2
+
+server s1 {
+	rxreq
+	barrier b4 sync
+	txresp
+} -start
+
+varnish v1 -vcl+backend {
+	sub vcl_recv {
+		if (req.url == "/2") {
+			return (synth(700));
+		}
+	}
+} -start
+
+varnish v1 -cliok "param.set feature +http2"
+
+client c1 {
+	stream 1 {
+		txreq -req GET -url /1 -hdr "content-length" "1" -nostrend
+		barrier b1 sync
+		barrier b2 sync
+		txdata -data 1
+#		rxwinup
+		barrier b3 sync
+		rxresp
+		expect resp.status == 200
+	} -start
+	stream 3 {
+		barrier b1 sync
+		txreq -req GET -url /2 -hdr "content-length" "1" -nostrend
+		barrier b2 sync
+		barrier b3 sync
+		txdata -data 2
+#		rxwinup
+		rxresp
+		expect resp.status == 700
+		barrier b4 sync
+	} -start
+} -run