layers: PR767, Fix crash exiting smoketest
layers: PR767, Fix crash exiting smoketest

Commit a86b57c caused a Windows crash when shutting down smoketest.
Command buffer cleanup for object bindings wasn't happening when
calling DestroyCommandPool.

Change-Id: Ie233763e37ed9bc6988dddbf932aa3eda2960940

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