layers: Fix VerifyCopyUpdateContents on combined image sampler descriptors
layers: Fix VerifyCopyUpdateContents on combined image sampler descriptors

A missing break at the end of the ImageSampler case results in falling
through to the Image case, leading to spurious validation errors such as:

  vkUpdateDescriptorsSets() failed copy update from Descriptor Set 0x108
  to Descriptor Set 0x137 with error: Attempted copy update to image
  descriptor failed due to: Invalid VkImageView: 0x100000000

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