Add riak_test for ring resizing during YZ operations

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

Note this test has a ring size reduction commented out which should be re-instated once the issue with YZ and ring sizing downward is resolve.