camera: Check if aux camera whitelist is set before restricting cameras

Some devices have a fully featured 3rd camera and adding 20+ camera apps
to the whitelist is impossible due to the string length limit on
systemprops. Add a check to see if the prop is even set, and if not,
check if the blacklist property is set and mark those apps to hide the
3rd camera from. If a package is not part of the blacklist, just restore
the original behaviour and expose all the cameras to the app.

Change-Id: I6c3b33c077e8710c73b5d0fa28e1b017d6c43a58