Automatic merge from submit-queue (batch tested with PRs 56579, 55236, 56512, 56549, 56538). 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>.
cleanup useless functions
cleanup some useless functions, for they get no references from others during my search. Please remind me if I'm wrong.