- Part of #653.
- No need for `defaultCommand` since ContainerService startup will write
a new launchd plist with the `start` subcommand included.
## Type of Change
- [ ] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Documentation update
## Motivation and Context
Allows us to add commands to support post-installation, migration, etc.
## Testing
- [x] Tested locally
- [ ] Added/updated tests
- [ ] Added/updated docs
Today if you do system stop twice (or if you forgot the server isn't
running) you get bombarded with annoying (and confusing) XPC interrupted
messages. We should skip the container stop and list dance if we can't
talk to the APIServer with a simple ping.