layers: Fixes to memory mapping checks
layers: Fixes to memory mapping checks

MapMemory w/ size 0 is now invalid in the spec so remove comment and
change callback to ERROR.
Update some error messages for clarity.
Only update the mapped memory range state if MapMemory succeeds.

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