[pom] Update mockito to 2.8.9

Author: hazendaz

pom.xml

@@ -216,7 +216,7 @@
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>2.7.22</version>
+      <version>2.8.9</version>
       <scope>test</scope>
     </dependency>
     <!-- Do not go to 2.x until we are on jdk7 -->