Document/kexec-kdump-howto.txt: improve notes for kdump_pre and kdump_post scripts
    
    upstream: fedora
    related:  bz2003832
    conflict: none
    
    commit 8cc51f3ab922cad5e857e37440d65466b1b8c2fd
    Author: Pingfan Liu <piliu@redhat.com>
    Date:   Mon Nov 15 22:23:42 2021 +0800
    
        Document/kexec-kdump-howto.txt: improve notes for kdump_pre and kdump_post scripts
    
        Signed-off-by: Pingfan Liu <piliu@redhat.com>
        Acked-by: Coiby Xu <coxu@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>