add annotation about IsLikelyNotMountPoint can't to distinguish mounts and symbolic link

pkg/util/mount/mount.go

@@ -53,7 +53,7 @@ type Interface interface {
 	// is a mountpoint.
 	// It should return ErrNotExist when the directory does not exist.
 	// IsLikelyNotMountPoint does NOT properly detect all mountpoint types
-	// most notably linux bind mounts.
+	// most notably linux bind mounts and symbolic link.
 	IsLikelyNotMountPoint(file string) (bool, error)
 	// DeviceOpened determines if the device is in use elsewhere
 	// on the system, i.e. still mounted.

pkg/util/mount/mount_linux.go

@@ -228,6 +228,7 @@ func (mounter *Mounter) IsMountPointMatch(mp MountPoint, dir string) bool {
 // IsLikelyNotMountPoint determines if a directory is not a mountpoint.
 // It is fast but not necessarily ALWAYS correct. If the path is in fact
 // a bind mount from one part of a mount to another it will not be detected.
+// It also can not distinguish between mountpoints and symbolic links.
 // mkdir /tmp/a /tmp/b; mount --bind /tmp/a /tmp/b; IsLikelyNotMountPoint("/tmp/b")
 // will return true. When in fact /tmp/b is a mount point. If this situation
 // if of interest to you, don't use this function...