buffet: fix the unit test.

Fix the unit test. refresh Access Token does not generate
Invalid Credentials any more.

BUG=b:38308727
TEST=unit test.

Change-Id: Ibac59cfdc203f1dd92f9371ede2742503d12b021
Reviewed-on: https://weave-review.googlesource.com/10010
Reviewed-by: Kan Yan <kyan@google.com>

src/device_registration_info_unittest.cc

diff --git a/src/device_registration_info_unittest.cc b/src/device_registration_info_unittest.cc
index 1be7984..03755d9 100644
--- a/src/device_registration_info_unittest.cc
+++ b/src/device_registration_info_unittest.cc
@@ -315,7 +315,6 @@
   ErrorPtr error;
   EXPECT_FALSE(RefreshAccessToken(&error));
   EXPECT_TRUE(error->HasError(kErrorDomainOAuth2, "invalid_grant"));
-  EXPECT_EQ(GcdState::kInvalidCredentials, GetGcdState());
   EXPECT_EQ(test_data::kDeviceId, dev_reg_->GetSettings().cloud_id);
 }