Update rook helm charts documentation

Signed-off-by: Karol Chrapek <kaarol@it-flow.pl>

Documentation/helm-operator.md

@@ -94,12 +94,13 @@ The following tables lists the configurable parameters of the rook-operator char
 | `rbacEnable`       | If true, create & use RBAC resources | `true`               |
 | `resources`        | Pod resource requests & limits       | `{}`                 |
 | `logLevel`         | Global log level        | `INFO`                 |
-| `agent.flexVolumeDirPath` | Path where the Rook agent discovers the flex volume plugins | `/usr/libexec/kubernetes/kubelet-plugins/volume/exec/` |
+| `agent.flexVolumeDirPath` | Path where the Rook agent discovers the flex volume plugins (*) | `/usr/libexec/kubernetes/kubelet-plugins/volume/exec/` |
 | `agent.toleration`        | Toleration for the agent pods | <none> |
 | `agent.tolerationKey`     | The specific key of the taint to tolerate | <none> |
 | `mon.healthCheckInterval` | The frequency for the operator to check the mon health | `45s` |
 | `mon.monOutTimeout`       | The time to wait before failing over an unhealthy mon | `300s` |
 
+&ast; For Kubernetes 1.9.x `agent.flexVolumeDirPath` should be changed to `/var/lib/kubelet/volumeplugins/`. [Flexvolume documentation](flexvolume.md#for-kubernetes--19x)
 
 ### Command Line
 You can pass the settings with helm command line parameters. Specify each parameter using the

cluster/charts/rook/values.yaml.tmpl

@@ -39,4 +39,5 @@ rbacEnable: true
 # agent:
 #   toleration: NoSchedule
 #   tolerationKey: key
+## For Kubernetes >= 1.9.x flexVolumeDirPath should be changed to /var/lib/kubelet/volumeplugins/
 #   flexVolumeDirPath: /usr/libexec/kubernetes/kubelet-plugins/volume/exec/