fix(auth): allow anyone to get cluster-info in kube-public

[xiaosuiba]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:

/kind bug

What this PR does / why we need it: According to official docs, anyone could read resources in kube-public namespace https://kubernetes.io/docs/reference/setup-tools/kubeadm/implementation-details/

Which issue(s) this PR fixes:

Fixes #1332

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[leoryu]

@metang326 please check this PR, thx.