Switch to a BLS configuration on %%post
    
    By default the old grubby tool isn't installed anymore and it's part of
    the grubby-deprecated package. Instead the grubby wrapper that modifies
    BLS config files is installed for backward compatiblity with old grubby.
    
    So on postinstall the bootloader configuration has to be changed to BLS
    since non-BLS bootloader configuration won't be updated anymore without
    the old grubby tool and the new-kernel-pkg script.
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>