use snooze directly in upr-consumer to avoid locking overhead

Change-Id: I01993956af864e6047f7503daea8e512f05ee44e
Reviewed-on: http://review.couchbase.org/37931
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: Sundararaman Sridharan <sundar@couchbase.com>