Fix to the bug in repositioning checkpoint cursors.

This bug can cause the data loss issues in TAP / UPR.

Change-Id: I1eda9f2d49a71ab5fe456d9b1e106794c4b50bce
Reviewed-on: http://review.couchbase.org/34667
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>