Use finit API to get runlevel instead of utmp

utmp is not available with musl libc

api.c

@@ -316,6 +316,11 @@ static void cb(uev_t *w, void *UNUSED(arg), int UNUSED(events))
 			result = do_handle_emit(rq.data, sizeof(rq.data));
 			break;
 
+		case INIT_CMD_GET_RUNLEVEL:
+			rq.runlevel = runlevel;
+			result = 0;
+			break;
+
 		case INIT_CMD_ACK:
 			_d("Client failed reading ACK.");
 			goto leave;