Revert "grub2: Exit gracefully if the configuration has BLS enabled"
Revert "grub2: Exit gracefully if the configuration has BLS enabled"

This reverts commit 985a14100295c99d0c6d712bfbee0ec52a3a1601.
It turned out that some people have old bootloaders, and hence
get the "no entries" problem.  That's much, much much worse
than double entries.

GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree