set exit status to 1 in the unknown si_code case

src/lxc/start.c

@@ -341,6 +341,7 @@ static int signal_handler(int fd, uint32_t events, void *data,
 			break;
 		default:
 			ERROR("Unknown si_code: %d", hdlr->init_died);
+			hdlr->exit_status = 1;
 		}
 	}