layers: Guard checks of pQueueFamilyIndices
layers: Guard checks of pQueueFamilyIndices

Only examine pQueueFamilyIndices if sharingMode is VK_SHARING_MODE_CONCURRENT
This fixes a crash in CTS when sharing mode was VK_SHARING_MODE_EXCLUSIVE
and queueFamilyIndexCount was VK_QUEUE_FAMILY_IGNORED

Change-Id: I72b1f140e8949e711723e98bdaead15655ab07a5

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