BUG/MINOR: http: don't log a 503 on client errors while waiting for requests

If a client aborts a request with an error (typically a TCP reset), we must
log a 400. Till now we did not set the status nor close the stream interface,
causing the request to attempt to be forwarded and logging a 503.

Should be backported to 1.4 which is affected as well.

src/proto_http.c

@@ -2334,6 +2334,8 @@ int http_wait_for_request(struct session *s, struct channel *req, int an_bit)
 				session_inc_http_err_ctr(s);
 			}
 
+			txn->status = 400;
+			stream_int_retnclose(req->prod, NULL);
 			msg->msg_state = HTTP_MSG_ERROR;
 			req->analysers = 0;