Don't attempt to tone map content that is already in range.

For content where the luminance values are able to be represented by
the destination we do not need to further reduce the luminance of
those values.

This CL also removes the clamp that enforces the actual luminance
values of the content don't exceed those defined in the metadata.
This fixes issues where the content and metadata don't match by favoring
the content value over the metadata.

Test: test app provided with the bug
Bug: 188531000
Change-Id: I12a65187d60c75167e1b1244e42b50ef3bb51bcd