CBQE-927: add check_items param in NewUpgradeBaseTest.verification

Change-Id: I3617e8b460be9b0291a93db70872ca2949e2cfde
Reviewed-on: http://review.couchbase.org/23984
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>