Check returned value (even if in practice it's always 0 atm)

tests/datawizard/acquire_release2.c

@@ -108,7 +108,7 @@ int main(int argc, char **argv)
 		if (ret == -ENODEV) goto enodev;
 		STARPU_CHECK_RETURN_VALUE(ret, "starpu_task_submit");
 
-                starpu_data_acquire_cb(token_handle, STARPU_R, callback, NULL);  // send
+                ret = starpu_data_acquire_cb(token_handle, STARPU_R, callback, NULL);  // send
 		STARPU_CHECK_RETURN_VALUE(ret, "starpu_data_acquire_cb");
 	}