Fix flaky unit test Test_Run_Positive_VolumeMountControllerAttachEnabledRace data race

ref: https://github.com/kubernetes/kubernetes/issues/94568

pkg/kubelet/volumemanager/reconciler/reconciler_test.go

@@ -48,14 +48,14 @@ import (
 const (
 	// reconcilerLoopSleepDuration is the amount of time the reconciler loop
 	// waits between successive executions
-	reconcilerLoopSleepDuration time.Duration = 1 * time.Nanosecond
+	reconcilerLoopSleepDuration = 1 * time.Nanosecond
 	// waitForAttachTimeout is the maximum amount of time a
 	// operationexecutor.Mount call will wait for a volume to be attached.
-	waitForAttachTimeout         time.Duration     = 1 * time.Second
-	nodeName                     k8stypes.NodeName = k8stypes.NodeName("mynodename")
-	kubeletPodsDir               string            = "fake-dir"
-	testOperationBackOffDuration time.Duration     = 100 * time.Millisecond
-	reconcilerSyncWaitDuration   time.Duration     = 10 * time.Second
+	waitForAttachTimeout         = 1 * time.Second
+	nodeName                     = k8stypes.NodeName("mynodename")
+	kubeletPodsDir               = "fake-dir"
+	testOperationBackOffDuration = 100 * time.Millisecond
+	reconcilerSyncWaitDuration   = 10 * time.Second
 )
 
 func hasAddedPods() bool { return true }
@@ -1791,6 +1791,7 @@ func Test_Run_Positive_VolumeMountControllerAttachEnabledRace(t *testing.T) {
 	<-stoppedChan
 
 	finished := make(chan interface{})
+	fakePlugin.Lock()
 	fakePlugin.UnmountDeviceHook = func(mountPath string) error {
 		// Act:
 		// 3. While a volume is being unmounted, add it back to the desired state of world
@@ -1812,6 +1813,7 @@ func Test_Run_Positive_VolumeMountControllerAttachEnabledRace(t *testing.T) {
 		close(finished)
 		return devicePath, nil
 	}
+	fakePlugin.Unlock()
 
 	// Start the reconciler again.
 	go reconciler.Run(wait.NeverStop)