Clock type in throttling is currently inferred by the ThrottleTimer's clock type even though it is a per-ThrottleGroup property; it doesn't make sense to have different clock types in the same group. Moving this to a field in ThrottleGroup can simplify some of the throttle functions. Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>