Add Exec interface to VolumeHost

This exec should be used by volume plugins to execute mount utilities.
It will eventually execute things in mount containers.

pkg/controller/volume/attachdetach/attach_detach_controller.go

@@ -571,6 +571,10 @@ func (adc *attachDetachController) GetConfigMapFunc() func(namespace, name strin
 	}
 }
 
+func (adc *attachDetachController) GetExec(pluginName string) mount.Exec {
+	return mount.NewOsExec()
+}
+
 func (adc *attachDetachController) addNodeToDswp(node *v1.Node, nodeName types.NodeName) {
 	if _, exists := node.Annotations[volumehelper.ControllerManagedAttachAnnotation]; exists {
 		keepTerminatedPodVolumes := false

pkg/controller/volume/persistentvolume/volume_host.go

@@ -93,6 +93,10 @@ func (adc *PersistentVolumeController) GetConfigMapFunc() func(namespace, name s
 	}
 }
 
+func (adc *PersistentVolumeController) GetExec(pluginName string) mount.Exec {
+	return mount.NewOsExec()
+}
+
 func (ctrl *PersistentVolumeController) GetNodeLabels() (map[string]string, error) {
 	return nil, fmt.Errorf("GetNodeLabels() unsupported in PersistentVolumeController")
 }