Cycles: Fix regular BVH not having proper visibility flags

This was caused by recent threading commit. Now because of all children
are set when they're ready need to explicitly update all parent's visibility.

intern/cycles/bvh/bvh_build.cpp

@@ -318,7 +318,7 @@ BVHNode* BVHBuild::run()
 			rootnode = NULL;
 			VLOG(1) << "BVH build cancelled.";
 		}
-		else if(!params.use_spatial_split) {
+		else {
 			/*rotate(rootnode, 4, 5);*/
 			rootnode->update_visibility();
 		}