CBQE-1056: fix verify_results when cluster's members were changed

Change-Id: I3395d60d58ddea2b6fbe45da7fe993a7487fe7df
Reviewed-on: http://review.couchbase.org/24768
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>