Automatic merge from submit-queue (batch tested with PRs 46686, 45049, 46323, 45708, 46487)
[Federation][kubefed]: Use StorageClassName for etcd pvc
This PR updates kubefed to use the StorageClassName field [added in 1.6](http://blog.kubernetes.io/2017/03/dynamic-provisioning-and-storage-classes-kubernetes.html
) for etcd's pvc to allow the user to specify which storage class they want to use. If no value is provided to ``kubefed init``, the field will not be set, and initialization of the pvc may fail on a cluster without a default storage class configured.
The alpha annotation that was previously used (``volume.alpha.kubernetes.io/storage-class``) was deprecated as of 1.4 according to the following blog post:
http://blog.kubernetes.io/2016/10/dynamic-provisioning-and-storage-in-kubernetes.html
**Release note**:
```
'kubefed init' has been updated to support specification of the storage class (via --etcd-pv-storage-class) for the Persistent Volume Claim (PVC) used for etcd storage. If --etcd-pv-storage-class is not specified, the default storage class configured for the cluster will be used.
```
cc: @kubernetes/sig-federation-pr-reviews
3e1d68624e