MB-10641 Starts from the first item on a collapsed checkpoint

If a given TAP replication cursor was sitting on an old closed
checkpoint and moved over to the collapsed checkpoint, then
the cursor should start from the first item on the collapsed
checkpoint, so that CHECKPOINT_START message with a new
checkpoint id should be sent to the destination node.

Change-Id: I62314ea402a0d5d7a525445b9e21f6227c9975ef
Reviewed-on: http://review.couchbase.org/34924
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>