10_linux_bls: don't add --users option to generated menu entries
    
    The generated menu entries have a --users $grub_users option but this will
    fail on old versions of GRUB, since it expects the --users option argument
    to either be a constant or a variable that has been set.
    
    The latest GRUB version fix this but the GRUB core isn't updated on a GRUB
    package update, so this will cause the entries to not be shown in the menu
    after a system upgrade.
    
    Since can cause issues and because the entries that weren't generated from
    the BLS snippets didn't have the --users option either, just don't add it.
    
    Resolves: rhbz#1693515
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>