This just prevents some annoying log messages from occurring during the cleanup stage of resizing when vnodes are being shut down. [This commit](https://github.com/basho/riak_core/commit/134e3ac9af6f76904e1a1580751445c59e8d8509) has more details (the messages mentioned are things like `merge_callback` that fired while the shutdown messages were being sent). If you remove it and run the `riak_test` it should still pass but you may see some `riak_kv_vnode` crashes because `{deleted, ModState}` is passed to `handle_command`.