plugin/kubernetes: Enable protobuf, Update client api package (#1114)

* vendor

* code

vendor/k8s.io/apimachinery/README.md

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+# apimachinery
+
+Scheme, typing, encoding, decoding, and conversion packages for Kubernetes and Kubernetes-like API objects.
+
+
+## Purpose
+
+This library is a shared dependency for servers and clients to work with Kubernetes API infrastructure without direct 
+type dependencies.  It's first comsumers are `k8s.io/kubernetes`, `k8s.io/client-go`, and `k8s.io/apiserver`.
+
+
+## Compatibility
+
+There are *NO compatibility guarantees* for this repository.  It is in direct support of Kubernetes, so branches
+will track Kubernetes and be compatible with that repo.  As we more cleanly separate the layers, we will review the
+compatibility guarantee.
+
+
+## Where does it come from?
+
+`apimachinery` is synced from https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/apimachinery.
+Code changes are made in that location, merged into `k8s.io/kubernetes` and later synced here.
+
+
+## Things you should *NOT* do
+
+ 1. Add API types to this repo.  This is for the machinery, not for the types.
+ 2. Directly modify any files under `pkg` in this repo.  Those are driven from `k8s.io/kuberenetes/staging/src/k8s.io/apimachinery`.
+ 3. Expect compatibility.  This repo is direct support of Kubernetes and the API isn't yet stable enough for API guarantees.