Support for ZFS, while desirable, is problematic with newer kernel
releases. The stable ZFS release seldom supports the current newest
kernel version, and this makes the new_kernel image basically useless as
it cannot be published, and is not often built with new kernel releases.
This uses a dirty workaround to work around the fact it is impossible to
remove a list item from a modules system list type. Since ZFS support is
conditional to being supported on the current platform, we can fake ZFS
not being supported *for the no-zfs build only*. This overlay is only
added when evaluating the image, nothing else.
