MB-9898: Add flow control entry points

Change-Id: Iea08194e3b0b3ee5da46df1dbbcd069ddfd17eda
Reviewed-on: http://review.couchbase.org/35430
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>