In addition to this line, `do_backend_delete` can also be called [here](https://github.com/basho/riak_kv/blob/8b814dafe95bf63ad4bfb7662a040333fcc38ba9/src/riak_kv_vnode.erl#L1727). I think it's safer to move the `maybe_cache_evict` call into `do_backend_delete`.