Default Ring Size in riak.conf should be 128 [JIRA: RIAK-3277]

[mikedotson]

Currently, the default ring_size in the riak.conf file is set to 64. This is a reasonable setting for clusters with nodes less than 6 nodes Cluster planning, however, a minimum of 5 nodes is recommended for a production Riak cluster Why Your Riak Cluster Should Have At Least Five Nodes.

Should the production cluster need to expand past the minimum 5 nodes (which is often the case as data and usage grows), there is no easy way to resize the ring from the default of 64 to 128. This would make a ring size of 128 a more appropriate default value for a production cluster.

While 128 is not optimal for test cluster sizes of less than 5 nodes, the impact on test clusters, should the default ring_size not be changed, would not be as much of an impact as it is on the production cluster.