layers: Fix core_validation issues GH103 and GH240
layers: Fix core_validation issues GH103 and GH240

Perform pipeline sample and attachment count validation at draw
time instead of vkCmdNextSubpass() time.  Also validate that
an active renderpass exists.

Change-Id: I912947287eef29d532519220750c3a93a3554565

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