Ejecting e.g. a USB stick removes it from the bus (bus power is removed),
but the last notification should be kept, otherwise a message like
"The device can be savely removed" immediately disappears.
Unfortunately it is almost impossible to tell when a device has been
physically removed (only indirectly, when a new device is plugged into
the same port), so allow some small leakage - in case the same device is
later replugged, no leakage happens.