MB-10856 Position the cursors correctly in collapsed checkpoints

Change-Id: I362f232640458420122f477943c6a6fe9da9ef0f
Reviewed-on: http://review.couchbase.org/36821
Tested-by: Sundararaman Sridharan <sundar@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>