vendor: update c/common to latest

Includes my DiskUsage() changes.

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

vendor/github.com/containers/common/libimage/layer_tree.go

@@ -141,19 +141,6 @@ func (r *Runtime) newLayerTreeFromData(images []*Image, layers []storage.Layer)
 	return &tree, nil
 }
 
-// layersOf returns all storage layers of the specified image.
-func (t *layerTree) layersOf(image *Image) []*storage.Layer {
-	var layers []*storage.Layer
-	node := t.node(image.TopLayer())
-	for node != nil {
-		if node.layer != nil {
-			layers = append(layers, node.layer)
-		}
-		node = node.parent
-	}
-	return layers
-}
-
 // children returns the child images of parent. Child images are images with
 // either the same top layer as parent or parent being the true parent layer.
 // Furthermore, the history of the parent and child images must match with the