Automatic merge from submit-queue (batch tested with PRs 53204, 53364, 53559, 53589, 53088). 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>.
Strip tokens from `kubeadm-config` config map
**What this PR does / why we need it**:
When kubeadm 1.8 create a cluster stores a `kubeadm-config` config map with all the info used for initialising the cluster.
This PR removes the kubeadm join token - which is a sensitive information - from this config map.
**Which issue this PR fixes**
[#485](https://github.com/kubernetes/kubeadm/issues/485)
**Special notes for your reviewer**:
This fixes all the subcommands that touch `kubeadm-config` config map, namely:
- kubeadm init
- kubeadm config upload
- kubeadm upgrade
```release-note
kubeadm: Strip bootstrap tokens from the `kubeadm-config` ConfigMap
```
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