unittests: Fixes unit tests for Windows (part 8)

Currently, there are some unit tests that are failing on Windows due to
various reasons:

- flexvolume coverts its paths to absolute paths, which means that on Windows the C:\ prefix
  will be added. This becomes an issue when prober.fs.Walk is called, which will join 2 absolute
  paths, both containing the C:\ prefix, resulting in an incorrect path.

pkg/volume/flexvolume/probe.go

@@ -228,6 +228,10 @@ func (prober *flexVolumeProber) updateEventsMap(eventDirAbs string, op volume.Pr
 // Each file or directory change triggers two events: one from the watch on itself, another from the watch
 // on its parent directory.
 func (prober *flexVolumeProber) addWatchRecursive(filename string) error {
+	// this may be called with an actual absolute path on Windows (with a C:\ prefix).
+	// But the prober.fs.Walk below will execute filepath.Join(fs.root, filenameAbove), which
+	// will result in an incorrect path, you can't join C:\path and C:\another\path.
+	filename = strings.TrimPrefix(filename, `C:\`)
 	addWatch := func(path string, info os.FileInfo, err error) error {
 		if err == nil && info.IsDir() {
 			if err := prober.watcher.AddWatch(path); err != nil {

pkg/volume/flexvolume/probe_test.go

@@ -72,11 +72,6 @@ func TestProberExistingDriverBeforeInit(t *testing.T) {
 
 // Probes newly added drivers after prober is running.
 func TestProberAddRemoveDriver(t *testing.T) {
-	// Skip tests that fail on Windows, as discussed during the SIG Testing meeting from January 10, 2023
-	if goruntime.GOOS == "windows" {
-		t.Skip("Skipping test that fails on Windows")
-	}
-
 	// Arrange
 	_, fs, watcher, prober := initTestEnvironment(t)
 	prober.Probe()
@@ -210,11 +205,6 @@ func TestEmptyPluginDir(t *testing.T) {
 
 // Issue an event to remove plugindir. New directory should still be watched.
 func TestRemovePluginDir(t *testing.T) {
-	// Skip tests that fail on Windows, as discussed during the SIG Testing meeting from January 10, 2023
-	if goruntime.GOOS == "windows" {
-		t.Skip("Skipping test that fails on Windows")
-	}
-
 	// Arrange
 	driverPath, fs, watcher, _ := initTestEnvironment(t)
 	err := fs.RemoveAll(pluginDir)
@@ -236,11 +226,6 @@ func TestRemovePluginDir(t *testing.T) {
 
 // Issue an event to remove plugindir. New directory should still be watched.
 func TestNestedDriverDir(t *testing.T) {
-	// Skip tests that fail on Windows, as discussed during the SIG Testing meeting from January 10, 2023
-	if goruntime.GOOS == "windows" {
-		t.Skip("Skipping test that fails on Windows")
-	}
-
 	// Arrange
 	_, fs, watcher, _ := initTestEnvironment(t)
 	// Assert