Comment # 20 on bug 1028136 from Daniel Molkentin

So this is not a dracut bug at all. Dracut just shadows the real problem:
Somehow, your swap device was reinitialized (did you run mkswap manually?)
yielding a new UUID. dracut updates this dynamically, but grub doesn't notice.
Can you run

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

and check if /boot/grub2/grub.conf now holds the correct UUID?