grubby-bls: always generate the BLS snippets when adding new entries
    
    a BLS file is generated at build time and stored in /lib/modules/$kernel
    but this default BLS file assumes that /boot is a mount point and so the
    kernel and initrd paths are relative to the root of this boot partition.
    
    This is not the case if /boot is not a mount point or if the bootloader
    is zipl, since zipl expects the absolute path to be in the BLS snippet.
    
    The kernel-install scripts takes care of this and modifies the BLS file
    if needed, but grubby doesn't do that. So instead just generate the BLS
    always even if there is one for the kernel version of the added entry.
    
    Resolves: rhbz#1653365
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>