Mark HPA REST Clients Flag as Deprecated

This marks the option to switch to Heapster for the HPA as deprecated.
It'll be removed next release when Heapster is retired.

cmd/kube-controller-manager/app/options/hpacontroller.go

@@ -47,6 +47,7 @@ func (o *HPAControllerOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.Float64Var(&o.HorizontalPodAutoscalerTolerance, "horizontal-pod-autoscaler-tolerance", o.HorizontalPodAutoscalerTolerance, "The minimum change (from 1.0) in the desired-to-actual metrics ratio for the horizontal pod autoscaler to consider scaling.")
 	fs.BoolVar(&o.HorizontalPodAutoscalerUseRESTClients, "horizontal-pod-autoscaler-use-rest-clients", o.HorizontalPodAutoscalerUseRESTClients, "If set to true, causes the horizontal pod autoscaler controller to use REST clients through the kube-aggregator, instead of using the legacy metrics client through the API server proxy.  This is required for custom metrics support in the horizontal pod autoscaler.")
 	fs.DurationVar(&o.HorizontalPodAutoscalerCPUInitializationPeriod.Duration, "horizontal-pod-autoscaler-cpu-initialization-period", o.HorizontalPodAutoscalerCPUInitializationPeriod.Duration, "The period after pod start when CPU samples might be skipped.")
+	fs.MarkDeprecated("horizontal-pod-autoscaler-use-rest-clients", "Heapster is no longer supported as a source for Horizontal Pod Autoscaler metrics.")
 	fs.DurationVar(&o.HorizontalPodAutoscalerInitialReadinessDelay.Duration, "horizontal-pod-autoscaler-initial-readiness-delay", o.HorizontalPodAutoscalerInitialReadinessDelay.Duration, "The period after pod start during which readiness changes will be treated as initial readiness.")
 }