Fixed panic in iSCSI.UnmountDevice

Fill iscsiDetacher.plugin so iscsiDetacher.plugin.targetLocks.LockKey(iqn) does not
panic.

pkg/volume/iscsi/attacher.go

@@ -137,6 +137,7 @@ type iscsiDetacher struct {
 	host    volume.VolumeHost
 	mounter mount.Interface
 	manager diskManager
+	plugin  *iscsiPlugin
 }
 
 var _ volume.Detacher = &iscsiDetacher{}
@@ -148,6 +149,7 @@ func (plugin *iscsiPlugin) NewDetacher() (volume.Detacher, error) {
 		host:    plugin.host,
 		mounter: plugin.host.GetMounter(iscsiPluginName),
 		manager: &ISCSIUtil{},
+		plugin:  plugin,
 	}, nil
 }
 
@@ -160,7 +162,7 @@ func (detacher *iscsiDetacher) Detach(volumeName string, nodeName types.NodeName
 }
 
 func (detacher *iscsiDetacher) UnmountDevice(deviceMountPath string) error {
-	unMounter := volumeSpecToUnmounter(detacher.mounter, detacher.host)
+	unMounter := volumeSpecToUnmounter(detacher.mounter, detacher.host, detacher.plugin)
 	err := detacher.manager.DetachDisk(*unMounter, deviceMountPath)
 	if err != nil {
 		return fmt.Errorf("iscsi: failed to detach disk: %s\nError: %v", deviceMountPath, err)
@@ -225,11 +227,11 @@ func volumeSpecToMounter(spec *volume.Spec, host volume.VolumeHost, targetLocks
 	}, nil
 }
 
-func volumeSpecToUnmounter(mounter mount.Interface, host volume.VolumeHost) *iscsiDiskUnmounter {
+func volumeSpecToUnmounter(mounter mount.Interface, host volume.VolumeHost, plugin *iscsiPlugin) *iscsiDiskUnmounter {
 	exec := host.GetExec(iscsiPluginName)
 	return &iscsiDiskUnmounter{
 		iscsiDisk: &iscsiDisk{
-			plugin: &iscsiPlugin{},
+			plugin: plugin,
 		},
 		mounter:    mounter,
 		exec:       exec,