Automatic merge from submit-queue (batch tested with PRs 39714, 39646)
use etcd2 as storage-backend for federation until federation features are completely tested with etcd3
**What this PR does / why we need it**: move federation etcd to etcd3
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#39594
**Special notes for your reviewer**: here is the [link](https://github.com/kubernetes/features/issues/44#issuecomment-270772674) to announcement making etcd3 as default
**Release note**:
```release-note
```
3888aca8ab