WIP: Add riak_test for ring-resizing during YZ operations

Do not merge until the downward ring-resize issue has been resolved.

Add yz_ring_resizing, which:

- Creates a 4-node cluster, ring size 16
- Sets up indexing using the "fruit" schema
- Loads up some data with bb
- Fires up an asynchronous query
- Resizes ring to 64
- Waits for ring resize to finish and checks query results
- Resized ring from 64 -> 32
- Waits for ring resize to finish and checks query results

Currently, the last 2 items are not working, and this is being investigated. Ring resizing upwards does work.