Improve error messages and remove check

* Improve error messages
  * remove a check for the existance of unmount target. We probably
    should not mask that the target was missing.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

mount/mount_windows.go

@@ -132,14 +132,6 @@ func (m *Mount) GetParentPaths() ([]string, error) {
 
 // Unmount the mount at the provided path
 func Unmount(mount string, flags int) error {
-	if _, err := os.Stat(mount); err != nil {
-		if os.IsNotExist(err) {
-			return nil
-		}
-
-		return fmt.Errorf("failed to access mount point %s: %w", mount, err)
-	}
-
 	mount = filepath.Clean(mount)
 	adsFile := mount + ":" + sourceStreamName
 	var layerPath string