protobuf: proto: upstream changes breaking compatibility with Kubernetes

https://github.com/golang/protobuf/commit/8cc9e46429bfb16289d40d30b2ee3f4923b47345 breaks compatibility with kubernetes.

https://github.com/golang/protobuf/blob/master/proto/table_unmarshal.go#L331 mandates that all struct fields have proto tags. The TypeMeta fields in kubernetes structs do not contain a proto tag, https://github.com/kubernetes/apiserver/blob/master/pkg/apis/audit/v1beta1/types.go#L145 is a typical example.

If this change is necessitated we should work to put it in a major revision and allow v1 to be compatible without tags.