uterm: vt: fix input-device sleep-control

uterm: vt: fix input-device sleep-control

We need to correctly put input devices asleep only if we really disable
the VT. If our callbacks fail and prevent the VT-switch, we must keep the
input devices awake. Otherwise, we will lose control over the
sleep-states.

Also correctly put the device asleep during shutdown.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>