1.6 will also default to protobuf encoding if using etcd3.  **This change is
irreversible.**  To rollback, you must restore from a backup made before the
protobuf/etcd3 switch, and any changes since the backup will be lost.  As 1.5
does not support protobuf encoding, if you roll back to 1.5 after upgrading to
protobuf you will be forced to restore from backup, and you will lose any changes
since you converted to protobuf.  After conversion to protobuf, you should

* kubeadm - fix upgrades with external etcd ([#63925](https://github.com/kubernetes/kubernetes/pull/63925), [@detiber](https://github.com/detiber))

* Update busybox image link to gcr.io for kube-proxy. ([#53818](https://github.com/kubernetes/kubernetes/pull/53818), [@MrHohn](https://github.com/MrHohn))
* Restores the ability to apply network policy objects against the networking.k8s.io/v1 API ([#54106](https://github.com/kubernetes/kubernetes/pull/54106), [@liggitt](https://github.com/liggitt))

		t.Fatalf("Could not get partial restore failures metric: %v", err)
	}
	if partialRestoreFailures != 0.0 {
		t.Errorf("Already did a partial resync? Something failed earlier!")
	}

	// Add a rule jumping from svc3's service chain to svc4's endpoint, then try to
	// delete svc4. This will fail because the partial resync won't rewrite svc3's
	// rules and so the partial restore would leave a dangling jump from there to

* kube-scheduler: restores default leader election behavior. leader-elect command line parameter should "true" ([#60524](https://github.com/kubernetes/kubernetes/pull/60524), [@dims](https://github.com/dims))

* Node-Problem-Detector configuration is now decoupled from the Kubernetes release on GKE/GCE. ([#73288](https://github.com/kubernetes/kubernetes/pull/73288), [@wangzhen127](https://github.com/wangzhen127))
* Restores --username and --password flags to kubectl ([#75451](https://github.com/kubernetes/kubernetes/pull/75451), [@liggitt](https://github.com/liggitt))

- github.com/certifi/gocertifi: [2c3bb06](https://github.com/certifi/gocertifi/tree/2c3bb06)
- github.com/checkpoint-restore/go-criu/v5: [v5.0.0](https://github.com/checkpoint-restore/go-criu/v5/tree/v5.0.0)
- github.com/cncf/udpa/go: [5459f2c](https://github.com/cncf/udpa/go/tree/5459f2c)
- github.com/cockroachdb/errors: [v1.2.4](https://github.com/cockroachdb/errors/tree/v1.2.4)

* Restores --username and --password flags to kubectl ([#75451](https://github.com/kubernetes/kubernetes/pull/75451), [@liggitt](https://github.com/liggitt))

* Fix kubelet PVC stale metrics ([#59170](https://github.com/kubernetes/kubernetes/pull/59170), [@cofyc](https://github.com/cofyc))
* Restores the ability of older clients to delete and scale jobs with initContainers ([#59880](https://github.com/kubernetes/kubernetes/pull/59880), [@liggitt](https://github.com/liggitt))

- github.com/cenkalti/backoff: [v2.1.1+incompatible](https://github.com/cenkalti/backoff/tree/v2.1.1)
- github.com/checkpoint-restore/go-criu: [bdb7599](https://github.com/checkpoint-restore/go-criu/tree/bdb7599)
- github.com/cheekybits/genny: [9127e81](https://github.com/cheekybits/genny/tree/9127e81)