kdump-lib.sh: replace '[ ]' with '[[ ]]' and get rid of legacy ``
    
    upstream: fedora
    resolves: bz2003832
    conflict:
        Patch hunk modified for function is_secure_boot_enforced().
    
    commit 30090f3a15d266937bba6ef2429876e26b5e92d7
    Author: Kairui Song <kasong@redhat.com>
    Date:   Mon Sep 13 01:17:05 2021 +0800
    
        kdump-lib.sh: replace '[ ]' with '[[ ]]' and get rid of legacy ``
    
        Updated file syntax with following command:
    
        sed -i -e 's/\(\s\)\[\s\([^]]*\)\s\]/\1\[\[\ \2 \]\]/g' kdump-lib.sh
        (replace '[ ]' with '[[ ]]')
    
        sed -i -e 's/`\([^`]*\)`/\$(\1)/g' kdump-lib.sh
        (replace `...` with $(...))
    
        And manually updated [[ ... -a ... ]] and [[ ... -o ... ]] with && and
        ||.
    
        Signed-off-by: Kairui Song <kasong@redhat.com>
        Acked-by: Philipp Rudo <prudo@redhat.com>
    
    Signed-off-by: Tao Liu <ltao@redhat.com>