Automatic merge from submit-queue (batch tested with PRs 55214, 55166). 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: don't create duplicate volume/mount

**What this PR does / why we need it**:
If certificates for etcd are located in the same directory or
subdirectories of kubernetes pki directory, don't create separate
volumes and mounts in manifests.

**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  kubernetes/kubeadm#522

**Special notes for your reviewer**:
/sig cluster-lifecycle 
/area kubeadm

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