dracut-kdump.sh: Use stat instead of ls to get vmcore size
    
    upstream: fedora
    resolves: bz2003832
    conflict: none
    
    commit b1c794a2cf1a4ed6c8fc2588d1e03ffcde07813c
    Author: Kairui Song <kasong@redhat.com>
    Date:   Tue Sep 14 03:00:48 2021 +0800
    
        dracut-kdump.sh: Use stat instead of ls to get vmcore size
    
        ls output is fragile, so use stat instead.
    
        Signed-off-by: Kairui Song <kasong@redhat.com>
        Acked-by: Philipp Rudo <prudo@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>