Automatic merge from submit-queue (batch tested with PRs 41540, 41808, 41710, 41838, 41840)
kubeadm: update token to use '.' in discovery pkg
**What this PR does / why we need it**: While working on getting https://github.com/kubernetes/community/pull/381 implemented, I noticed the kubeadm discovery pkg was printing out tokens incorrectly. Corrected and fixed up corresponding test.
**Special notes for your reviewer**: /cc @luxas @jbeda
**Release note**:
```release-note
NONE
```
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