Fix to unit tests.

...et/floodlightcontroller/core/internal/ControllerTest.java

...troller/devicemanager/internal/DeviceManagerImplTest.java

...ller/linkdiscovery/internal/LinkDiscoveryManagerTest.java

...loodlightcontroller/threadpool/MockScheduledExecutor.java

...loodlightcontroller/threadpool/MockThreadPoolService.java

...t/floodlightcontroller/topology/TopologyInstanceTest.java

...et/floodlightcontroller/topology/TopologyManagerTest.java