layers: GH7, Fix bad var names in threading layer
layers: GH7, Fix bad var names in threading layer

Change-Id: Iabfd7900a934162a425008593ecc0f0b4d56476e

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools