Update test dependency of sentinel-cluster-server-default

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

sentinel-cluster/sentinel-cluster-server-default/pom.xml

@@ -35,5 +35,16 @@
             <groupId>io.netty</groupId>
             <artifactId>netty-all</artifactId>
         </dependency>
+
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 </project>