Fix wrong reuse of riak_client processes
Fix wrong reuse of riak_client processes

Manifests may exists in different bag for each bucket, use new one to
map/reduce each bucket and fetch manifest objects in it.

basho/riak_cs,GabrielNicolasAvellaneda/riak_cs,GabrielNicolasAvellaneda/riak_cs,sdebnath/riak_cs,yangchengjian/riak_cs,yangchengjian/riak_cs,basho/riak_cs,laurenrother/riak_cs,dragonfax/riak_cs,laurenrother/riak_cs,laurenrother/riak_cs,laurenrother/riak_cs,basho/riak_cs,dragonfax/riak_cs,sdebnath/riak_cs,basho/riak_cs,sdebnath/riak_cs,dragonfax/riak_cs,GabrielNicolasAvellaneda/riak_cs,GabrielNicolasAvellaneda/riak_cs,yangchengjian/riak_cs,sdebnath/riak_cs,dragonfax/riak_cs,yangchengjian/riak_cs