SUBMARINE-107. Reduce the scope of mockito-core in submarine to test. Contributed by kevin su.

hadoop-submarine/pom.xml

@@ -44,6 +44,7 @@
         <groupId>org.mockito</groupId>
         <artifactId>mockito-core</artifactId>
         <version>2.23.4</version>
+        <scope>test</scope>
       </dependency>
 
       <dependency>