squash: also squash systemctl if switch-root is not needed
    
    systemctl need to be accessible on switch-root, but we unmount the
    squash image on switch-root, so it will fail. systemctl depends on a lot
    of libraries, squash them can save more RAM. So allow modules
    (eg. kdump) to tell dracut that switch-root will be intercepted,
    then we don't need to take care of that.
    
    Signed-off-by: Kairui Song <kasong@redhat.com>
    (cherry picked from commit 3ee0ca5eb74be5d1fbd0e6d643f6fff06234177f)
    
    Resolves: #1691705
    
    patch_name: 0020.patch
    present_in_specfile: true
    location_in_specfile: 20
    squash_commits: true