Make writethrough transfer idle fetches

We don't actually need them urgently

src/datawizard/write_back.c

@@ -64,7 +64,7 @@ void _starpu_write_through_data(starpu_data_handle_t handle, unsigned requesting
 
 				struct _starpu_data_request *r;
 				r = _starpu_create_request_to_fetch_data(handle, &handle->per_node[node],
-									 STARPU_R, 1, 1, wt_callback, handle, 0, "_starpu_write_through_data");
+									 STARPU_R, 2, 1, wt_callback, handle, 0, "_starpu_write_through_data");
 
 			        /* If no request was created, the handle was already up-to-date on the
 			         * node */