Fix bandwidth reporting when doing a restarted download with "-r".
The offset is already accounted for in xs->lastrcvd and doesn't
have to be subtracted again.
Reported by: Florian Smeets <flo@smeets.im>
Submitted by: Mateusz Guzik <mjguzik@gmail.com>
Tested by: Florian Smeets <flo@smeets.im>
MFC after: 1 week