grubby-bls: use id instead of title to get the default entry
    
    The wrapper is using the title before to store the default entry, but we
    are now using the entry id for grub2, so make the wrapper query the id.
    
    Resolves: rhbz#1638103
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>