Modify NewVolumeManager() function return value

Since function NewVolumeManager() will always return vm and nil, we do not need the second return value, it will always be nil.

pkg/kubelet/kubelet_test.go

@@ -283,7 +283,7 @@ func newTestKubeletWithImageList(
 	require.NoError(t, err, "Failed to initialize VolumePluginMgr")
 
 	kubelet.mounter = &mount.FakeMounter{}
-	kubelet.volumeManager, err = kubeletvolume.NewVolumeManager(
+	kubelet.volumeManager = kubeletvolume.NewVolumeManager(
 		controllerAttachDetachEnabled,
 		kubelet.nodeName,
 		kubelet.podManager,
@@ -296,7 +296,6 @@ func newTestKubeletWithImageList(
 		kubelet.recorder,
 		false, /* experimentalCheckNodeCapabilitiesBeforeMount*/
 		false /* keepTerminatedPodVolumes */)
-	require.NoError(t, err, "Failed to initialize volume manager")
 
 	// enable active deadline handler
 	activeDeadlineHandler, err := newActiveDeadlineHandler(kubelet.statusManager, kubelet.recorder, kubelet.clock)