auth: Refactor how authentication methods are passed to server/auth library.

server/auth/authtest/method.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package authtest
 
 import (
         "errors"
         "net/http"
         "net/url"
@@ skipping 15 matching lines @@
 // Authenticate returns predefined User object (if it is not nil) or error.
 func (m FakeAuth) Authenticate(context.Context, *http.Request) (*auth.User, error) {
         if m.User == nil {
                 return nil, ErrAuthenticationError
         }
         return m.User, nil
 }
 
 // LoginURL returns fake login URL.
 func (m FakeAuth) LoginURL(c context.Context, dest string) (string, error) {
-        return "http://fake/login?dest=" + url.QueryEscape(dest), nil
+        return "http://fake.example.com/login?dest=" + url.QueryEscape(dest), nil
 }
 
 // LogoutURL returns fake logout URL.
 func (m FakeAuth) LogoutURL(c context.Context, dest string) (string, error) {
-        return "http://fake/logout?dest=" + url.QueryEscape(dest), nil
+        return "http://fake.example.com/logout?dest=" + url.QueryEscape(dest), nil
 }