Merge pull request #57658 from andyxning/code_refactor

Automatic merge from submit-queue. 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>.

Remove CgroupParent from RunContainerOptions

**What this PR does / why we need it**:
`CgroupParent` argument for a container is derived from sandbox config instead of container config in [dockershim](https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/dockershim/helpers_linux.go#L125-L132). The logic to get `cgroupParent` for container is useless.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:
I may be wrong for only considering docker runtime. But according to cri runtime api, only [`LinuxPodSandboxConfig` has a field `CgroupParent`](https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/apis/cri/v1alpha1/runtime/api.pb.go#L590). So i think it is only valid in sandbox config.

BTW, maybe we also need to delete [`CgroupParent` field in `RunContainerOptions` struct](https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/container/runtime.go#L432).
**Release note**:

```release-note
None
```

pkg/kubelet/container/runtime.go

@@ -444,8 +444,6 @@ type RunContainerOptions struct {
 	// this directory will be used to create and mount the log file to
 	// container.TerminationMessagePath
 	PodContainerDir string
-	// The parent cgroup to pass to Docker
-	CgroupParent string
 	// The type of container rootfs
 	ReadOnly bool
 	// hostname for pod containers

pkg/kubelet/kubelet_pods.go

@@ -461,8 +461,6 @@ func (kl *Kubelet) GenerateRunContainerOptions(pod *v1.Pod, container *v1.Contai
 		return nil, nil, err
 	}
 
-	cgroupParent := kl.GetPodCgroupParent(pod)
-	opts.CgroupParent = cgroupParent
 	hostname, hostDomainName, err := kl.GeneratePodHostNameAndDomain(pod)
 	if err != nil {
 		return nil, nil, err