Automatic merge from submit-queue (batch tested with PRs 64945, 64977). 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>.

fix kubeadm init does not inform the users it is pulling images

**What this PR does / why we need it**:
Kubeadm should print a message informing the user that it is pre-pulling images before starting the init sequence, making users aware of the action in progress, which can take some time in environments with poor internet connection.

**Which issue(s) this PR fixes**:
fixes https://github.com/kubernetes/kubeadm/issues/908

**Release note**:
```release-note
NONE
```