Switch to BLS in tools package %post scriptlet
The switch to a BLS configuration was made before in the grubby package
%post scriptlet, but this is wrong since it means that a not up-do-date
grub2-switch-to-blscfg script could be used to do the switch.
Resolves: rhbz#1652806
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>