[1/2] Improve flash availability check.

* 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 handler 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 is fine.

PS2: Post the action, need to let OS load camera after boot. 10 seconds is fine.
PS3: Use simple overlay, default false.

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