Use exact brightnesses values for comparison.

Using BrightnessSynchronizer introduced an epsilon value in the
comparison. This meant it was possible for brightness changes to never
reach min or max if they were made in sufficiently small steps. Given:

1) The need to reach both min and max brightnesses.

2) The increased resolution of brightness controls on devices.

3) The desire to make the framework as independent as possible of
brightness resolution.

we no longer allow for an epsilon delta.

Fixes: 191935286
Test: manual

Change-Id: Ie4872fa81aa6f23799cd6b4dfdbfd2a61ec6ce7a