Further refactoring of LinkDiscoveryManager.

src/main/java/net/floodlightcontroller/core/IOFSwitch.java

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

...et/floodlightcontroller/linkdiscovery/ILinkDiscovery.java

...lightcontroller/linkdiscovery/ILinkDiscoveryListener.java

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

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