Notify checkpoint creation events to paused UPR conns

- Notify these events to corresponding paused upr
connections along with tap connections.

Change-Id: I0c820c48953f63d590a7538041ae68b1b382a251
Reviewed-on: http://review.couchbase.org/39367
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>