collect workload and scheduler stats

Change-Id: Ie09c5d4095d0f393e479f0f0e73ac8c66bfbc6a8
Reviewed-on: http://review.couchbase.org/40441
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Tested-by: Pavel Paulau <pavel.paulau@gmail.com>