CBQE-927: offline_cluster_upgrade_and_reboot test

Change-Id: Ie54ae0ee75560936f85d0de8754988f5a3edeaf1
Reviewed-on: http://review.couchbase.org/23659
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>