Why do we need the two special cases for `resize` and `abort_resize` here? Is the "not invalid" catch-all case on [line 502](https://github.com/basho/riak_core/blob/7fc16113303b28b606eb68f07775e7c4a64247b6/src/riak_core_claimant.erl#L502) not work? Will we ever have invalid members involved in a transfer?