Fix wake and scan behavior

- Add wakelock for driver start/stop to ensure a wifilock
  acquisition kick starts driver. Also cleaned up state machine
  driver start/stop behavior.
- Add periodic scans when driver is started to ensure wifi
  reconnections when wifilock exists or when user chooses
  never to sleep
- some minor clean up

Change-Id: I844eb70491d5aa2f8c8933b3d8dd01ba237ee534