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/export_unsafe.go

@@ -1,35 +0,0 @@
-// Copyright 2017, 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.
-
-// +build !purego
-
-package cmp
-
-import (
-	"reflect"
-	"unsafe"
-)
-
-const supportExporters = true
-
-// retrieveUnexportedField uses unsafe to forcibly retrieve any field from
-// a struct such that the value has read-write permissions.
-//
-// The parent struct, v, must be addressable, while f must be a StructField
-// describing the field to retrieve. If addr is false,
-// then the returned value will be shallowed copied to be non-addressable.
-func retrieveUnexportedField(v reflect.Value, f reflect.StructField, addr bool) reflect.Value {
-	ve := reflect.NewAt(f.Type, unsafe.Pointer(uintptr(unsafe.Pointer(v.UnsafeAddr()))+f.Offset)).Elem()
-	if !addr {
-		// A field is addressable if and only if the struct is addressable.
-		// If the original parent value was not addressable, shallow copy the
-		// value to make it non-addressable to avoid leaking an implementation
-		// detail of how forcibly exporting a field works.
-		if ve.Kind() == reflect.Interface && ve.IsNil() {
-			return reflect.Zero(f.Type)
-		}
-		return reflect.ValueOf(ve.Interface()).Convert(f.Type)
-	}
-	return ve
-}