loader: Use loader_GetInstanceProcAddr
loader: Use loader_GetInstanceProcAddr

By using the vkGetInstanceProcAddr function in the loader's
instance dispatch table we will trace that function
during initialization of layers. Don't want to do that so
call loader internal function.

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