[1/2] Improve led availability checking and caching.

* Not sure if camera will be available at boot completed to let invoke its objects, if so should be good.
  If not i'll add a hadler to post the action by 10-15 seconds after boot completed.
  EDIT: Post the action, need to let OS load camera after boot. 10 seconds should be fine.

PS2: Use simple overlay.

Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>

Don't use camera way.