CBQE-927: restart entire cluster after offline upgrade

Change-Id: I121bbd289483e5a0f2110891bd3b1c291583d926
Reviewed-on: http://review.couchbase.org/24094
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>