Add LauncherProtocol to K8s resource manager client

private val launcherBackend = new LauncherBackend() {
  override protected def conf: SparkConf = sparkConf  override def onStopRequest(): Unit = {
    if (isClusterMode && appId != null) {
      yarnClient.killApplication(appId)
    } else {
      setState(SparkAppHandle.State.KILLED)
      stop()
    }
  }
}