CBQE-0: fix append xdcr test

Change-Id: If6c02df5526e9d22c97a4007cde790bf01e3b7e4
Reviewed-on: http://review.couchbase.org/29605
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>