Add flavor to switch setup phase
Use PB connection for manifest bag
Reduce number of nodes

Because there are only foru riak cs nodes.
It's possible to increase but defered for future task.
Add flavor description to riak_test/README
Cosmetics

- objects/blocks instead of manifest/block
- add specs
- log message
Merge pull request #872 from basho/feature/riak-test-flavor

Feature/riak_test flavor

Reviewed-by: kuenishi