Remove k8s.io/kubernetes dependency from multus

Fix #675

vendor/k8s.io/client-go/rest/plugin.go

@@ -47,6 +47,13 @@ type AuthProviderConfigPersister interface {
 	Persist(map[string]string) error
 }
 
+type noopPersister struct{}
+
+func (n *noopPersister) Persist(_ map[string]string) error {
+	// no operation persister
+	return nil
+}
+
 // All registered auth provider plugins.
 var pluginsLock sync.Mutex
 var plugins = make(map[string]Factory)
@@ -69,5 +76,8 @@ func GetAuthProvider(clusterAddress string, apc *clientcmdapi.AuthProviderConfig
 	if !ok {
 		return nil, fmt.Errorf("no Auth Provider found for name %q", apc.Name)
 	}
+	if persister == nil {
+		persister = &noopPersister{}
+	}
 	return p(clusterAddress, apc.Config, persister)
 }