fedup F21 to Rawhide fails, couldn't get boot images

[Chris Murphy]

OK yay grubby+btrfs silent error, where the grub.cfg isn't updated. OK
so I do this myself and then I get a kernel panic. Near as I can tell
the i386 vmlinuz-fedup kernel, and i386 initramfs-fedup.img aren't
compatible. They're definitely loaded (found by grub) but kablewy,
well before systemd even comes into play. Classic Unable to mount root
fs on unknown-block(0,0).

Sounds to me like it doesn't know what Btrfs is. I wonder if btrfs.mod
is being baked into the fedup initramfs....

Chris Murphy