CBQE-1621 add api for zone testing

Change-Id: I1003a7c24757c95700c1e08eacbc17fa1a73f60a
Reviewed-on: http://review.couchbase.org/30081
Tested-by: Thuan Nguyen <soccon@gmail.com>
Reviewed-by: Tommie McAfee <tommie@couchbase.com>