new cluster spec for xdcr testing

Change-Id: Ie728ae14973f1a68b787c7651e8bc01c6ac7d6dc
Reviewed-on: http://review.couchbase.org/43101
Reviewed-by: Venu Uppalapati <venumahesh@gmail.com>
Tested-by: Venu Uppalapati <venumahesh@gmail.com>