* Adding support for Block Volume type to rbd plugin. ([#56651](https://github.com/kubernetes/kubernetes/pull/56651), [@sbezverk](https://github.com/sbezverk))

  ```sh
  $ kubectl get event
  LAST SEEN   TYPE     REASON              OBJECT                        MESSAGE
  <unknown>   Normal   Scheduled           pod/nginx-6c975b59f8-gvmjr    Successfully assigned default/nginx-6c975b59f8-gvmjr to minikube
  
  $ kubectl describe pod xxx
  ......
  Events:
    Type    Reason     Age        From               Message

    * If the serialization type is application/vnd.kubernetes.protobuf, and protobuf marshaling is not implemented for the requested API resource type, a '406 Not Acceptable is returned'.
    * If the serialization type is 'application/json':

    * as the certificates expiration approaches.

* kube-apiserver: the default `--endpoint-reconciler-type` is now `lease`. The `master-count` endpoint reconciler type is deprecated and will be removed in 1.13. ([#63383](https://github.com/kubernetes/kubernetes/pull/63383), [@liggitt](https://github.com/liggitt))

        * `kubernetes.io/hostname`
        * `kubernetes.io/instance-type`
        * `kubernetes.io/os`
        * `kubernetes.io/arch`
        * `beta.kubernetes.io/instance-type`
        * `beta.kubernetes.io/os`
        * `beta.kubernetes.io/arch`
        * `failure-domain.kubernetes.io/zone`

- Adjusts the fsType for cinder values to be `ext4` if no fsType is specified. ([#90608](https://github.com/kubernetes/kubernetes/pull/90608), [@huffmanca](https://github.com/huffmanca)) [SIG Storage]

Also, please note:
- using `application/vnd.kubernetes.protobuf` as the media storage type for 1.6 is default but not required
- the ability to rollback to etcd2 can be preserved by setting the storage media type flag on `kube-apiserver`

  ```
  --storage-media-type application/json
  ```

  to continue to use `application/json` as the storage media type which can be changed to
  `application/vnd.kubernetes.protobuf` at a later time.