Automatic merge from submit-queue
Kubeadm: print information about certificates
Prints basic information about certificates to the user.
Example of `kubeadm init` output:
```
<master/pki> generated Certificate Authority key and certificate:
Issuer: CN=kubernetes | Subject: CN=kubernetes | CA: true
Not before: 2016-09-30 11:19:19 +0000 UTC Not After: 2026-09-28 11:19:19 +0000 UTC
Public: /etc/kubernetes/pki/ca-pub.pem
Private: /etc/kubernetes/pki/ca-key.pem
Cert: /etc/kubernetes/pki/ca.pem
<master/pki> generated API Server key and certificate:
Issuer: CN=kubernetes | Subject: CN=kube-apiserver | CA: false
Not before: 2016-09-30 11:19:19 +0000 UTC Not After: 2017-09-30 11:19:19 +0000 UTC
Alternate Names: [172.18.76.239 10.0.0.1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local]
Public: /etc/kubernetes/pki/apiserver-pub.pem
Private: /etc/kubernetes/pki/apiserver-key.pem
Cert: /etc/kubernetes/pki/apiserver.pem
<master/pki> generated Service Account Signing keys:
Public: /etc/kubernetes/pki/sa-pub.pem
Private: /etc/kubernetes/pki/sa-key.pem
```
Example of `kubeadm join` command:
```
<node/csr> received signed certificate from the API server:
Issuer: CN=kubernetes | Subject: CN=system:node:minion | CA: false
Not before: 2016-09-30 11:28:00 +0000 UTC Not After: 2017-09-30 11:28:00 +0000 UTC
```
Fixes#33642
cc @kubernetes/sig-cluster-lifecycle
347d448180