MB-11741: Better scheduling of checkpointRemoverTask

Waking up the checkpoint Remover Task once the cursors
complete parsing a checkpoint till the end, helps
prevent retaining blob instances for a longer time
than necessary.

Change-Id: Ieb1435dafac2e9b9984664218d6761c6c807333a
Reviewed-on: http://review.couchbase.org/40355
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>