[atomic] GRUB2 config generation broken in Fedora 22 GA

[Colin Walters <walters verbum org>]

Hi, see:

https://bugzilla.redhat.com/show_bug.cgi?id=1226520

# atomic run cgwalters/ostree-grub2-fix

Should either validate or help you fix it.  The fixed ostree
made it into the main updates stream, so once you've successfully
updated, future updates should succeed reliably.

There is some planning talk around regenerating images regularly,
and once that's done, it will include the fixed version by default.