Postpone VDP_Init() until we need it. Zero in the meantime.

bin/varnishd/cache/cache_req.c

@@ -131,7 +131,7 @@ Req_New(const struct worker *wrk, struct sess *sp)
 	p = (void*)PRNDUP(p + sizeof(*req->htc));
 
 	req->vdc = (void*)p;
-	VDP_Init(req->vdc);
+	memset(req->vdc, 0, sizeof *req->vdc);
 	p = (void*)PRNDUP(p + sizeof(*req->vdc));
 
 	req->htc = (void*)p;

bin/varnishd/cache/cache_req_fsm.c

@@ -425,6 +425,7 @@ cnt_transmit(struct worker *wrk, struct req *req)
 		sendbody = 1;
 	}
 
+	VDP_Init(req->vdc);
 	if (req->filter_list == NULL)
 		req->filter_list = resp_Get_Filter_List(req);
 	if (req->filter_list == NULL ||