Add buffering to the log audit backend
Add buffering to the log audit backend

Signed-off-by: Mik Vyatskov <vmik@google.com>

Kubernetes-commit: 881e6d4f6f905079b2c27299e7b631b6903b6815

kubernetes-nightly/sample-apiserver,kubernetes-nightly/sample-apiserver,kubernetes/sample-apiserver,kubernetes/sample-apiserver