skip updating /etc/default/grub for s390x
    
    Resolves: bz2104534
    Upstream: Fedora
    Conflict: None
    
    commit e8ae8975958d2b2d2a5f3853d82cdd95ef4bb653
    Author: Coiby Xu <coxu@redhat.com>
    Date:   Tue Jul 12 14:06:25 2022 +0800
    
        skip updating /etc/default/grub for s390x
    
        Resolves: bz2104534
    
        When running "kdumpctl reset-crashkernel --kernel=ALL" on s390x,
        sed: can't read /etc/default/grub: No such file or directory
        sed: can't read /etc/default/grub: No such file or directory
    
        This happens because s390x doesn't use the grub bootloader and
        /etc/default/grub doesn't exist.
    
        Reported-by: smitterl@redhat.com
        Reviewed-by: Philipp Rudo <prudo@redhat.com>
        Signed-off-by: Coiby Xu <coxu@redhat.com>
    
    Signed-off-by: Coiby Xu <coxu@redhat.com>