MINOR: http: Call http_send_name_header with the stream instead of the txn

This is just a minor change to ease integrartion of the HTX.
diff --git a/src/proto_http.c b/src/proto_http.c
index c93afa9..9678d51 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -3646,10 +3646,10 @@
  * for being forwarded. This is the reason why it rewinds the buffer before
  * proceeding.
  */
-int http_send_name_header(struct http_txn *txn, struct proxy* be, const char* srv_name) {
+int http_send_name_header(struct stream *s, struct proxy* be, const char* srv_name) {
 
 	struct hdr_ctx ctx;
-
+	struct http_txn *txn = s->txn;
 	char *hdr_name = be->server_id_hdr_name;
 	int hdr_name_len = be->server_id_hdr_len;
 	struct channel *chn = txn->req.chn;