h2: Give the h2 transport its waiting list steps

For now they do nothing that wouldn't happen in their absence.

Author: dridi

bin/varnishd/cache/cache_hash.c

@@ -398,7 +398,7 @@ hsh_reembark(struct worker *wrk, struct req *req)
 		req->top->topreq->transport->reembark(wrk, req);
 
 	if (req->transport->reembark != NULL) {
-		// For ESI includes
+		// For ESI includes or h2 streams
 		req->transport->reembark(wrk, req);
 		return;
 	}

bin/varnishd/http2/cache_http2_session.c

@@ -438,6 +438,28 @@ h2_new_session(struct worker *wrk, void *arg)
 	wrk->vsl = NULL;
 }
 
+/**********************************************************************
+ */
+
+static void
+h2_waitlist(struct worker *wrk, struct req *req)
+{
+
+	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
+	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
+}
+
+static void
+h2_reembark(struct worker *wrk, struct req *req)
+{
+
+	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
+	CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
+
+	if (IS_TOPREQ(req))
+		AZ(Pool_Task(req->sp->pool, req->task, TASK_QUEUE_RUSH));
+}
+
 struct transport HTTP2_transport = {
 	.name =			"HTTP/2",
 	.magic =		TRANSPORT_MAGIC,
@@ -447,4 +469,6 @@ struct transport HTTP2_transport = {
 	.req_body =		h2_req_body,
 	.req_fail =		h2_req_fail,
 	.sess_panic =		h2_sess_panic,
+	.waitlist =		h2_waitlist,
+	.reembark =		h2_reembark,
 };