core: fix re-realization of cgroup siblings
    
    This is a fix-up for eef85c4a3f8054d29383a176f6cebd1ef3a15b9a which
    broke this.
    
    Tracked down by @w-simon
    
    Fixes: #14453
    (cherry picked from commit 65f6b6bdcb500c576674b5838e4cc4c35e18bfde)
    
    Related: #1818054
    
    patch_name: 0348-core-fix-re-realization-of-cgroup-siblings.patch
    present_in_specfile: true
    location_in_specfile: 348
    squash_commits: true