Update the kubelet with the ability to register itself with the master.

I like a single flag that tells the path to a kubernetes_auth file better than calling BindClientConfigFlags because it allows clients to be portable across clusters with different auth setups, and facilitates rotating credentials.   Consider replacing client.BindClientConfigFlags with:
```go
import  "github.com/GoogleCloudPlatform/kubernetes/pkg/clientauth"
...
vars(
    authPath                = flag.String("auth_path", "", "Path to .kubernetes_auth file, specifying how to authenticate to API server.")
    apiServer               = flag.String("api_server", "Kubernetes API server (ip:port)")
)
...
func getApiserverClient() (*client.Client, error) {
    authInfo, err := clientauth.LoadFromFile(*authPath)
    if err != nil {
        return nil, err
    }
    clientConfig, err := authInfo.MergeWithConfig(client.Config{})
    if err != nil {
        return nil, err
    }
    clientConfig.Host = apiServer
    if c, err := client.New(&clientConfig); err != nil {
        return nil, err
    } else {
        return c, nil
    }
}
... 
apiClient, err := getApiserverClient()
```