Update vendor files to point to kubernetes-1.12.0-beta.1

vendor/google.golang.org/appengine/socket/doc.go

@@ -0,0 +1,10 @@
+// Copyright 2012 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+// Package socket provides outbound network sockets.
+//
+// This package is only required in the classic App Engine environment.
+// Applications running only in App Engine "flexible environment" should
+// use the standard library's net package.
+package socket