MB-8903: Switch defines from bytes to bits

Change-Id: Ic136a651c4e0f2563084b637693c9a25cd082cc6
Reviewed-on: http://review.couchbase.org/29407
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>