MB-10400: use wait_for_seqno_persistence for xdcr checkpointing

Change-Id: Id9d83497e3d5aa914832266f704b3704c9ec3c8d
Reviewed-on: http://review.couchbase.org/34806
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>