Automatic merge from submit-queue
Use variadic nature of *cobra.Command.AddCommand to add group of commands to a parent command
**What this PR does / why we need it**:
Rather than looping over commands in a group and add it one by one to a
parent command, use variadic nature of *cobra.Command.AddCommand to add
the group of commands to the parent.
Rather than looping over commands in a group and add it one by one to a
parent command, use variadic nature of *cobra.Command.AddCommand to add
the group of commands to the parent.
**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
```