BUG/MINOR: proto_htx: Reset to_forward value when a message is set to DONE

Because we try to forward infinitly message body, when its state is set to DONE,
we must be sure to reset to_foward value of the corresponding
channel. Otherwise, some errors can be errornously triggered.

No need to backport this patch.
diff --git a/src/proto_htx.c b/src/proto_htx.c
index 23a6fae..e27f24e 100644
--- a/src/proto_htx.c
+++ b/src/proto_htx.c
@@ -1253,6 +1253,7 @@
 		goto missing_data_or_waiting;
 
 	msg->msg_state = HTTP_MSG_DONE;
+	req->to_forward = 0;
 
   done:
 	/* other states, DONE...TUNNEL */
@@ -2183,6 +2184,7 @@
 		goto missing_data_or_waiting;
 
 	msg->msg_state = HTTP_MSG_DONE;
+	res->to_forward = 0;
 
   done:
 	/* other states, DONE...TUNNEL */