core/cgroup: fix return value of unit_cgorup_freezer_action()
    
    We should return 0 only if current freezer state, as reported by the
    kernel, is already the desired state. Otherwise, we would dispatch
    return dbus message prematurely in bus_unit_method_freezer_generic().
    
    Thanks to Frantisek Sumsal for reporting the issue.
    
    (cherry picked from commit d910f4c2b2542544d7b187a09605da7a0f220837)
    
    Related: #1830861
    
    patch_name: 0425-core-cgroup-fix-return-value-of-unit_cgorup_freezer_.patch
    present_in_specfile: true
    location_in_specfile: 425
    squash_commits: true