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Automatic merge from submit-queue (batch tested with PRs 57735, 57503). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>. Ensure virtual nodes aren't stranded in GC graph Fixes #56121 See https://github.com/kubernetes/kubernetes/issues/56121#issuecomment-353265160 for details on the sequence of events that can lead to virtual nodes getting stranded in the graph ```release-note Fixed garbage collection hang ``` (a branch with a commit that reliably triggers the cascading deletion test failure is at https://github.com/liggitt/kubernetes/commits/gc-debug-cascading... it's not easily made into a permanent test case because it only works when that test is run in isolation, and requires plumbing test hooks deep into the watch cache layer)