Skip some more durability test when not on mock

Change-Id: I69575f136fc85ed44143dda1bd0fc38d008548d9
Reviewed-on: http://review.couchbase.org/28188
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>