Add flush and close notify function to auditWriter
Add flush and close notify function to auditWriter

Problem:
Deleting a namespace with audit logging enabled hangs, when use kubectl to delete namespace, it will call some api, include delete namespace, get namespace, get namespace with watch=true, when call watch=true, the server will use responseWriter flush function to flush data to the client, now we don't have the flush function for auditWriter, which will hang when calling API with watch=true, in some case it will also call the closeNotify function

Solution:
Add flush and closeNotify function

Issue:
https://github.com/rancher/rancher/issues/17027

rancher/rancher,rancher/rancher,cjellick/rancher,cjellick/rancher,rancherio/rancher,cjellick/rancher,rancherio/rancher,rancher/rancher,rancher/rancher