Automatic merge from submit-queue (batch tested with PRs 61118, 60579). 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>.
Increase apiserver mem-threshold in density test
Ref: https://github.com/kubernetes/kubernetes/issues/60500#issuecomment-372682659 (fixes part of that issue)
/sig scalability
/kind bug
/priority important-soon
/cc @wojtek-t
/cc @crassirostris (for the release-note)
```release-note
Audit logging with buffering enabled can increase apiserver memory usage (e.g. up to 200MB in 100-node cluster). The increase is bounded by the buffer size (configurable). Ref: issue #60500
```
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