CBQE-0: wait_for_persistence returns status verified

Change-Id: I14f571f91298ca14ef41637329da10766f99ecc2
Reviewed-on: http://review.couchbase.org/35066
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>