- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Steps to reproduce this issue

1. 提交PR，Travis CI build failed，原因为单元测试不通过
![image](https://user-images.githubusercontent.com/33019873/80856713-bcd40180-8c7e-11ea-8a26-d50021587e85.png)
2. 单元测试要求直接报异常
![image](https://user-images.githubusercontent.com/33019873/80856717-d412ef00-8c7e-11ea-88a3-620b86ddecbe.png)
3. 5月1号解决[#5916]时，将默认方法修改了，现在不会报异常出来
![image](https://user-images.githubusercontent.com/33019873/80856741-0de3f580-8c7f-11ea-8bc8-c527e78d9e04.png)

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

Travis CI build 可以通过

*
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.common.config.configcenter;
import org.apache.dubbo.common.URL;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.DEFAULT_THREAD_POOL_KEEP_ALIVE_TIME;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.DEFAULT_THREAD_POOL_PREFIX;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.DEFAULT_THREAD_POOL_SIZE;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.PARAM_NAME_PREFIX;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.THREAD_POOL_KEEP_ALIVE_TIME_PARAM_NAME;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.THREAD_POOL_PREFIX_PARAM_NAME;
import static org.apache.dubbo.common.config.configcenter.AbstractDynamicConfiguration.THREAD_POOL_SIZE_PARAM_NAME;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNull;
import static org.junit.jupiter.api.Assertions.assertThrows;
/**
 * {@link AbstractDynamicConfiguration} Test
 *
 * @since 2.7.5
 */
public class AbstractDynamicConfigurationTest {