Wrap fsnotify errors in flexvolume and filesystem

Wrap fsnotify errors in flexvolume and filesystem so both flexvolume and kube-proxy can use the improved error logging.

pkg/util/filesystem/watcher.go

@@ -18,6 +18,7 @@ package filesystem
 
 import (
 	"context"
+	"fmt"
 
 	"github.com/fsnotify/fsnotify"
 )
@@ -65,7 +66,7 @@ func (w *fsnotifyWatcher) Init(eventHandler FSEventHandler, errorHandler FSError
 	var err error
 	w.watcher, err = fsnotify.NewWatcher()
 	if err != nil {
-		return err
+		return fmt.Errorf("fsnotify watcher init: %w", err)
 	}
 
 	w.eventHandler = eventHandler

pkg/volume/flexvolume/probe.go

@@ -257,7 +257,7 @@ func (prober *flexVolumeProber) initWatcher() error {
 		klog.Errorf("Received an error from watcher: %s", err)
 	})
 	if err != nil {
-		return fmt.Errorf("error initializing watcher: %s", err)
+		return fmt.Errorf("flex volume: %w", err)
 	}
 
 	if err := prober.addWatchRecursive(prober.pluginDir); err != nil {