Downgrade Kubernetes vendor version

Multus community decide that multus support the Kubernetes that
Kubernetes community supports, so changed vendor code to the
oldest version of currently supported.

vendor/github.com/google/go-cmp/cmp/internal/flags/flags.go

@@ -1,9 +0,0 @@
-// Copyright 2019, The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE.md file.
-
-package flags
-
-// Deterministic controls whether the output of Diff should be deterministic.
-// This is only used for testing.
-var Deterministic bool