drbd: fix WRITE_ACKED_BY_PEER_AND_SIS to not set RQ_NET_DONE

Just because this request happened during a resync does
not mean it may pretend to have been barrier-acked.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>