Upgrade Mockito to build on JDK10 (prometheus#375)

Signed-off-by: Silvio Moioli <smoioli@suse.de>

Author: moio

simpleclient_hibernate/pom.xml

@@ -59,7 +59,7 @@
         <dependency>
             <groupId>org.mockito</groupId>
             <artifactId>mockito-core</artifactId>
-            <version>2.6.8</version>
+            <version>2.18.0</version>
             <scope>test</scope>
         </dependency>