tests: Fix DisabledIndependentBlend attachments
tests: Fix DisabledIndependentBlend attachments

Add proper number of attachments so the number in the renderpass
matches the number in the subpass.  Fixes hang on AMD driver

Change-Id: I7caab7b95d5ce40c9caeda79866d10374f24cdc4

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