**What this PR does / why we need it**:
Makes functions in validation/schema.go private to kubectl,
further isolating kubectl.
**Which issue this PR fixes**
Part of a series of PRs to address kubernetes/community#598
**Release note**:
```release-note
NONE
```
**What this PR does / why we need it**:
Visibility rules allow dependency control. The rules currently in
place make all targets public, to override the default state of
private. This PR removes public visibility from kubectl code. It
uses specially named pacakge groups to identify "bad" dependencies on
kubectl code for later refactoring or removal.
**Which issue this PR fixes**
First in a series of PRs to address kubernetes/community#598
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue
log info on invalid --output-version
**Release note**:
``` release-note
release-note-none
```
Object versions default to the current version (v1) when a specified
`--output-version` is invalid. This patch logs a warning when this is
the case. Cases affected are all commands with the `--output-version`
option, and anywhere runtime objects are converted to versioned objects.
**Example**
```
$ kubectl get pod <mypod> -o json --output-version=invalid
W1013 17:24:16.810278 26719 result.go:238] info: the output version
specified (invalid) is invalid, defaulting to v1
{
"kind": "Pod",
"apiVersion": "v1",
"metadata": {
"name": "mypod",
"namespace": "test",
...
```
Object versions default to the current version (v1) when a specified
`--output-version` is invalid. This patch logs a warning when this is
the case. Cases affected are all commands with the `--output-version`
option, and anywhere runtime objects are converted to versioned objects.
**Example**
```
$ kubectl get pod <mypod> -o json --output-version=invalid
W1013 17:24:16.810278 26719 result.go:238] info: the output version
specified (invalid) is invalid, defaulting to v1
{
"kind": "Pod",
"apiVersion": "v1",
"metadata": {
"name": "mypod",
"namespace": "test",
...
```
