drbd: Silenced compiler warnings

Since version 4.6.1 gcc warns about variables that get
a value assigned, but which are never read later on.

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

diff --cc drivers/block/drbd/drbd_actlog.c
Simple merge

diff --cc drivers/block/drbd/drbd_receiver.c
Simple merge

diff --cc drivers/block/drbd/drbd_req.c
Simple merge

diff --cc drivers/block/drbd/drbd_state.c
Simple merge