camera2: Fix Nakasi crash-on-start when using Camera2 API.

Bug: 17252693

- WAR to ensure setMeteringAreas and setFocusAreas is never called
  if the max areas is 0.
- Fix AF handling for when there are no AF modes that support
  Camera#autoFocus being called.

Change-Id: Id2517b76e1be51f8adeeee30dc2032e03debed01