Apply timeout for powerdown event and reset state machine when bluez crashes

The powerdown event was missed some time for unknown reasons and bluez could
crash for unknown reasons. We will debug on the issue. But for the time
being, we add a powerdown timer and process power up event to recover from
bluez crash
bug 5239719

Change-Id: Ie7315fb01e029747951e1a97a2d2f1dce53a997b