updated default longhorn volume plugin path

proposed/longhorn/v0.1.0/questions.yml

@@ -47,7 +47,7 @@ questions:
   required: true
   label: Default Storage Class
 - variable: persistence.flexvolumePath
-  default: "/usr/libexec/kubernetes/kubelet-plugins/volume/exec/"
+  default: "/var/lib/kubelet/volumeplugins"
   description: "For GKE uses `/home/kubernetes/flexvolume/` instead, users can find the correct directory by running `ps aux|grep kubelet` on the host and check the --volume-plugin-dir parameter.  If there is none, the default `/usr/libexec/kubernetes/kubelet-plugins/volume/exec/` will be used."
   type: string
   label: Longhorn Flexvolume Path