message: Fix unit test failure
  This unit test was seen to fail on some machines. This fix makes sure that HMIToMobileResult does not return an older cached value defined earlier in the show_test class.
diff: @@ -720,6 +720,7 @@ TEST_F(ShowRequestTest, Run_MainField4_MetadataTag) {
  }
  TEST_F(ShowRequestTest, Run_MainField1_MetadataTagWithNoFieldData) {
  + Mock::VerifyAndClearExpectations(&mock_message_helper_);
  MessageSharedPtr msg = CreateMsgParams();
  SharedPtr<ShowRequest> command(CreateCommand<ShowRequest>(msg));
  @@ -744,6 +745,10 @@ TEST_F(ShowRequestTest, Run_MainField1_MetadataTagWithNoFieldData) {
  Event event(hmi_apis::FunctionID::UI_Show);
  event.set_smart_object(*ev_msg);
  + EXPECT_CALL(mock_message_helper_,
  + HMIToMobileResult(hmi_apis::Common_Result::SUCCESS))
  + .WillOnce(Return(mobile_apis::Result::SUCCESS));
  +
  MessageSharedPtr ui_command_result;
  EXPECT_CALL(
  app_mngr_,
  @@ -759,6 +764,8 @@ TEST_F(ShowRequestTest, Run_MainField1_MetadataTagWithNoFieldData) {
  (*ui_command_result)[am::strings::msg_params][am::strings::result_code]
  .asInt(),
  static_cast<int32_t>(mobile_apis::Result::WARNINGS));
  +
  + Mock::VerifyAndClearExpectations(&mock_message_helper_);
  }
  TEST_F(ShowRequestTest, Run_MediaClock_SUCCESS) {
  