Automatic merge from submit-queue (batch tested with PRs 48572, 48838, 48931, 48783, 47090)
kubeadm: change the default bootstrap token TTL to 24 hours
**What this PR does / why we need it**:
This PR changes the TTL for the default bootstrap token generated by `kubeadm init` (without the `--token-ttl` parameter) and `kubeadm token create` (without the `--ttl` flag). Previously, the default TTL was infinite. After this change it is 24 hours.
~~The reasoning for 2 hours as a default is that it's 1) long enough that someone manually using kubeadm (copy-pasting) shouldn't have any issues and 2) short enough that if something is going to break, it should break while the user/admin is still paying attention to the cluster. I'm open to bikeshedding about the exact value, 2 hours is a bit of a strawman.~~
**Edit: updated this to 24 hours instead of 2 hours.**
This is a breaking change if you rely on infinite TTL tokens (e.g., if you had an ASG group of worker nodes). The old behavior is easily restored by passing `--token-ttl 0` to `kubeadm init` or the `--ttl 0` flag to `kubeadm token create`.
**Which issue this PR fixes**: fixes https://github.com/kubernetes/kubeadm/issues/343
**Special notes for your reviewer**:
This was discussed earlier today in SIG-cluster-lifecycle
**Release note**:
```release-note
Change the default kubeadm bootstrap token TTL from infinite to 24 hours. This is a breaking change. If you require the old behavior, use `kubeadm init --token-ttl 0` / `kubeadm token create --ttl 0`.
```
cc @jbeda
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