libpack fix for networking extensions

libpack.patch

diff --git a/vendor/src/github.com/docker/libpack/tree.go b/vendor/src/github.com/docker/libpack/tree.go
index 89d8a18..3b236c1 100644
--- a/vendor/src/github.com/docker/libpack/tree.go
+++ b/vendor/src/github.com/docker/libpack/tree.go
@@ -16,6 +16,7 @@ func treeDel(repo *git.Repository, tree *git.Tree, key string) (*git.Tree, error
        key = TreePath(key)
        base, leaf := path.Split(key)

+       root := tree
        if tree != nil {
                if tree, err = TreeScope(repo, tree, base); err != nil {
                        return nil, err
@@ -36,12 +37,10 @@ func treeDel(repo *git.Repository, tree *git.Tree, key string) (*git.Tree, error
                return nil, err
        }

-       newTree, err := lookupTree(repo, treeId)
-       if err != nil {
-               return nil, err
+       if base == "" {
+               return lookupTree(repo, treeId)
        }
-
-       return newTree, err
+       return treeAdd(repo, root, key, treeId, false)
 }

 // treeAdd creates a new Git tree by adding a new object