MB-100: rem extra verification in offline_cluster_upgrade_non_default_path

Change-Id: Id83e223eaf60b92afe20a18ec4b9c2fbf742fb51
Reviewed-on: http://review.couchbase.org/24009
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>