Explicitly remove child cgroups

Under some circumstances, the base cgroup cannot be removed because its child cgroups still exist. This should take care of the issue.

@zack Could you check this works for you?

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nope, it still fails for me, but this time with a different error (repeated many times for different sub-groups), e.g.:

FileNotFoundError: [Errno 2] No such file or directory: '/sys/fs/cgroup/user.slice/user-1000.slice/user@1000.service/app.slice/app-org.gnome.Terminal.slice/swh.graph@272345/pv@13'

I finally found the actual issue, solved by !687 (merged)

closed