Merge pull request #36310 from irfanurrehman/federation-kubefed-todo-1

Automatic merge from submit-queue

[Federation] Make federation etcd PVC size configurable

This one implements one of the many TODO items pending in the previous set of kubefed PRs.
The design doc PR is at https://github.com/kubernetes/kubernetes/pull/34484

cc  @kubernetes/sig-cluster-federation  @madhusudancs



**Release note**:
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``` 
[Federation] kubefed init now has a new flag, --etcd-pv-capacity, which can be used to configure the persistent volume capacity for etcd.  
```

hack/verify-flags/known-flags.txt

@@ -174,6 +174,7 @@ etcd-config
 etcd-keyfile
 etcd-mutation-timeout
 etcd-prefix
+etcd-pv-capacity
 etcd-quorum-read
 etcd-server
 etcd-servers