Destroy instance correctly

Change-Id: Icf5f70e9436d75f335aea7fb7a9b971e50413e06
Reviewed-on: http://review.couchbase.org/25765
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>