Move persistence cursor into list of all cursors

We have a lot of duplicate code for handling the persistence and
tap cursors. All of this code functions in the same way so it's
better if we just keep all of the cursors in the checkpoint manager
in one place.

Change-Id: Ifab7331a7e0ef7b8528a6e3323847acd1e14caa9
Reviewed-on: http://review.couchbase.org/41459
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>