Blender Git Loki

Fix T82351: Cycles: Tile stealing glitches with adaptive sampling

In my testing this works, but it requires me to remove the min(start_sample...) part in the
adaptive sampling kernel, and I assume there's a reason why it was there?

Reviewed By: brecht

Maniphest Tasks: T82351

Differential Revision: https://developer.blender.org/D9445