Add expiration LRU cache for webhook token authenticator.

plugin/pkg/auth/authenticator/token/webhook/webhook_test.go

@@ -140,7 +140,7 @@ func newTokenAuthenticator(serverURL string, clientCert, clientKey, ca []byte) (
 	if err := json.NewEncoder(tempfile).Encode(config); err != nil {
 		return nil, err
 	}
-	return New(p)
+	return New(p, 0)
 }
 
 func TestTLSConfig(t *testing.T) {