Fixed metadata in disneymaterial

The metadata of DisneyMaterialLayer is the same with the one of
disneybdrf so the get_input_metadata of the later class has
been used as refactoring.

Also during the previous PR some metadata from DisneyMaterialFactory
was removed, because I thought it was not needed.

Signed-off-by: Marius Avram <marius.avram1309@gmail.com>
Sorry, I didn't understand what you meant when we discussed it.
Wouldn't it be better to change the default value in the DisneyBRDF metadata instead?