Comment # 3 on bug 1196062 from Takashi Iwai

(In reply to Jon Harrison from comment #2)
> Downloading kernel-default-base (download size 30.46 MiB)

This is it.  That's no kernel-default, but kernel-default-base, which is a
stripped version that is only suitable for VM or such things.  This conflicts
with the proper kernel-default package.

So uninstall kernel-default-base, and re-install kernel-default instead.