Merge pull request #62412 from bhcleek/go1.10

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

generated code should pass go vet for go1.10

**What this PR does / why we need it**:

Update code generator and the code it generates to pass `go vet`.

go1.10 runs `go vet` whenever `go test` is run. Because of this, generated code for CRDs needs to pass `go vet`.

**Release note**:

```release-note
Code generated for CRDs now passes `go vet`.
```

Kubernetes-commit: 5dde701b876d1d0915314c3ed146e986c4327f7e

vendor/k8s.io/apimachinery/pkg/runtime/serializer/versioning/versioning.go

@@ -166,9 +166,22 @@ func (c *codec) Decode(data []byte, defaultGVK *schema.GroupVersionKind, into ru
 // Encode ensures the provided object is output in the appropriate group and version, invoking
 // conversion if necessary. Unversioned objects (according to the ObjectTyper) are output as is.
 func (c *codec) Encode(obj runtime.Object, w io.Writer) error {
-	switch obj.(type) {
-	case *runtime.Unknown, runtime.Unstructured:
+	switch obj := obj.(type) {
+	case *runtime.Unknown:
 		return c.encoder.Encode(obj, w)
+	case runtime.Unstructured:
+		// avoid conversion roundtrip if GVK is the right one already or is empty (yes, this is a hack, but the old behaviour we rely on in kubectl)
+		objGVK := obj.GetObjectKind().GroupVersionKind()
+		if len(objGVK.Version) == 0 {
+			return c.encoder.Encode(obj, w)
+		}
+		targetGVK, ok := c.encodeVersion.KindForGroupVersionKinds([]schema.GroupVersionKind{objGVK})
+		if !ok {
+			return runtime.NewNotRegisteredGVKErrForTarget(objGVK, c.encodeVersion)
+		}
+		if targetGVK == objGVK {
+			return c.encoder.Encode(obj, w)
+		}
 	}
 
 	gvks, isUnversioned, err := c.typer.ObjectKinds(obj)