dracut-early-kdump.sh: make it POSIX compatible
    
    upstream: fedora
    resolves: bz2003832
    conflict: none
    
    commit 4c39ad9a0c9808a9b791a3e446d0b209ceccdc5e
    Author: Kairui Song <kasong@redhat.com>
    Date:   Mon Sep 13 16:40:25 2021 +0800
    
        dracut-early-kdump.sh: make it POSIX compatible
    
        Refactor and remove bash only syntax.
    
        Signed-off-by: Kairui Song <kasong@redhat.com>
        Acked-by: Philipp Rudo <prudo@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>