BUG/MINOR: proto_htx: Send outgoing data to client to start response processing

In http_wait_for_response(), we wait that all outgoing data have really been
sent (from the channel's point of view) to start the processing of the
response. In fact, it is used to send all intermediate 10x responses. For now
the HTX api is not really handy when multiple messages are stored in the HTX
structure.
diff --git a/src/proto_htx.c b/src/proto_htx.c
index 8520347..00712d3 100644
--- a/src/proto_htx.c
+++ b/src/proto_htx.c
@@ -1450,7 +1450,7 @@
 	 * we should only check for HTTP status there, and check I/O
 	 * errors somewhere else.
 	 */
-	if (unlikely(htx_is_empty(htx) || htx_get_tail_type(htx) < HTX_BLK_EOH)) {
+	if (unlikely(co_data(rep) || htx_is_empty(htx) || htx_get_tail_type(htx) < HTX_BLK_EOH)) {
 		/*
 		 * First catch invalid response
 		 */