h2: add vtc for VSV00011

Check for correct handling of missing pseudo-headers, and invalid
characters.
Signed-off-by: Asad Sajjad Ahmed <asadsa@varnish-software.com>

bin/varnishtest/tests/f00011.vtc

+varnishtest "H2: Empty pseudo-headers"
+
+server s1 {
+	rxreq
+	txresp
+} -start
+
+varnish v1 -arg "-p feature=+http2" -vcl+backend {
+} -start
+
+client c1 {
+	stream 1 {
+		txreq -url ""
+		rxrst
+	} -run
+} -run
+
+client c1 {
+	stream 1 {
+		txreq -url " \t"
+		rxrst
+	} -run
+} -run
+
+client c1 {
+	stream 1 {
+		txreq -scheme ""
+		rxrst
+	} -run
+} -run
+
+client c1 {
+	stream 1 {
+		txreq -scheme " \t"
+		rxrst
+	} -run
+} -run
+
+client c1 {
+	stream 1 {
+		txreq -req ""
+		rxrst
+	} -run
+} -run
+
+client c1 {
+	stream 1 {
+		txreq -req " \t"
+		rxrst
+	} -run
+} -run