Blender Git Loki

Cycles: Experiment with replacing Sharp Glossy with GGX when Filter Glossy is used

The idea is to make it simpler to remove noise from scenes when some prop uses
Sharp glossy closure and causes noise in certain cases. Previously Sharp Glossy
was not affected by Filter Glossy at all, which was quite confusing.

Here is a file which demonstrates the issue: {F417797}

After applying the patch all the noise from the scene is gone.

This change also solves fireflies reported in T50700.

Reviewers: brecht, lukasstockner97

Differential Revision: https://developer.blender.org/D2416