Automatic merge from submit-queue

Fix getting cgroup pids

Fixes https://github.com/kubernetes/kubernetes/issues/35214, https://github.com/kubernetes/kubernetes/issues/33232

Verified manually, but I didn't have time to run all the e2e's yet (will check it in the morning).

This should be cherry-picked into 1.4, and merged into 1.5 (/cc @saad-ali )

```release-note
Fix fetching pids running in a cgroup, which caused problems with OOM score adjustments & setting the /system cgroup ("misc" in the summary API).
```

/cc @kubernetes/sig-node