nspawn: rework how we allocate/kill scopes
    
    Fixes: #6347
    (cherry picked from commit 1d78fea2d6230e0aafa2603abc8f1f51966ef134)
    
    Resolves: #1697893
    
    patch_name: 0115-nspawn-rework-how-we-allocate-kill-scopes.patch
    present_in_specfile: true
    location_in_specfile: 115
    squash_commits: true