Always use instanceof before casting

...n/java/net/floodlightcontroller/counter/CounterStore.java

...tcontroller/devicemanager/internal/DeviceManagerImpl.java

...main/java/net/floodlightcontroller/firewall/Firewall.java

...ntroller/linkdiscovery/internal/LinkDiscoveryManager.java

...a/net/floodlightcontroller/loadbalancer/LoadBalancer.java

...va/net/floodlightcontroller/topology/TopologyManager.java