Camera: Update exposure drawables to fix various problems

Updates exposure drawables to new ones more similar to the
original AOSP drawables. Also makes them visible on light
backgrounds.

They were previously changed in change 28836.

Change-Id: I1c628980e809e48646c7a6a68a546255e2a09b80
Merge "Camera: Update exposure drawables to fix various problems" into cm-10.1
Merge remote branch 'cm/cm-10.1'