fast cluster convergence

[seanjensengrey]

Coordinate with @paegun on speeding up adding nodes under Riak KV and TS

https://github.com/basho/internal_wiki/wiki/Riak-Test-Rapid-Cluster-Convergence

relevant finding extracted from wiki page

[
  {riak_core,
    [
      {cluster_mgr, {"127.0.0.1", 10016} }, %%<< this is normally configured, so is helpful in finding the riak_core section
      {vnode_parallel_start, RING_SIZE},
      {forced_ownership_handoff, RING_SIZE},
      {handoff_concurrency, RING_SIZE}
    ]
  },
  {riak_repl,
    [ ... ] %%<< riak_repl is also normally configured and elided here just to provide context enough
  }
}.