Don't clobber immutable samplers in update
Don't clobber immutable samplers in update

The copy cases were already doing the right thing; the basic updates
missed the check for the sampler being immutable.

Fixes #2569

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers