Fix incorrect specification.
Fix incorrect specification.

Fix an incorrect type specification generating errors when running
dialyzer.

sargun/riak_ensemble,sargun/riak_ensemble,ricardobcl/riak_ensemble,basho/riak_ensemble,basho/riak_ensemble,cmeiklejohn/riak_ensemble,cmeiklejohn/riak_ensemble,ricardobcl/riak_ensemble