Add kernel-install scripts
    
    Install a 20-grubby.install and 90-loaderentry.install kernel-install
    scripts in /etc/kernel/install.d so these have higher precedence than
    the ones installed in /usr/lib/kernel/install.d by the systemd pkg.
    
    If GRUB 2 pkg isn't installed, then the systemd scripts are executed
    on kernel installation and removal.
    
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>