Step down if local_put fails in leader worker
Step down if local_put fails in leader worker

In riak_ensemble_peer:put_obj/4 when local_put/4 fails, step down by
sending a 'request_failed' message to the leader.

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