Camera: Disable Camera Launcher when both Front and Back sensors are not detected

Instead of checking only back sensor, this change checks both Front and Back sensors
at the time of first time boot up and then if no sensors are present, disable all
camera activities/CameraLauncher.

Ported from http://review.evervolv.com/#/c/8926/

Change-Id: Ic9ebd3140caa8df079fe01553d62e96207f2e159