Automatic merge from submit-queue (batch tested with PRs 64338, 64219, 64486, 64495, 64347). 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>.
kubeadm: conditionally set the kubelet cgroup driver for Docker
**What this PR does / why we need it**:
Add a new utility file - util/cgroupdriver.go.
Currently it only contains the public function GetCgroupDriverDocker().
The function uses 'docker info' to obtain the cgroup driver
for Docker.
On a later stage this file can contain more methods for different
CRI.
Use GetCgroupDriverDocker() in phases/kubelet/flags.go
to conditionally set the 'cgroup-driver' argument. On error
print a warning and don't set the argument value.
Add unit tests in cgroupdriver_test.go.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixeskubernetes/kubeadm#844
**Special notes for your reviewer**:
NONE
**Release note**:
```release-note
kubeadm: conditionally set the kubelet cgroup driver for Docker
```
/area kubeadm
/kind enhancement
@kubernetes/sig-cluster-lifecycle-pr-reviews
@luxas
87dfadb27a