Add wrappers for the module module

service/module/interface.go

+// Copyright 2016 The Chromium 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 module
+
+// Interface is the interface for all of the package methods which normally
+// would be in the 'module' package.
+type Interface interface {
+        List() ([]string, error)
+        NumInstances(module, version string) (int, error)
+        SetNumInstances(module, version string, instances int) error
+        Versions(module string) ([]string, error)
+        DefaultVersion(module string) (string, error)
+        Start(module, version string) error
+        Stop(module, version string) error
+}