vendor: Update golang.org/x/net/ipv6

vendor/golang.org/x/net/ipv6/ipv6_test.go

@@ -0,0 +1,22 @@
+// 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 file.
+
+package ipv6
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+var disableTests = false
+
+func TestMain(m *testing.M) {
+	if disableTests {
+		fmt.Fprintf(os.Stderr, "ipv6 tests disabled in Go 1.9 until netreflect is fixed (Issue 19051)\n")
+		os.Exit(0)
+	}
+	// call flag.Parse() here if TestMain uses flags
+	os.Exit(m.Run())
+}