Merge into master from pull request #2255:

...t/floodlightcontroller/devicemanager/internal/Device.java

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

...odlightcontroller/devicemanager/web/DeviceSerializer.java

src/main/java/net/floodlightcontroller/packet/DHCP.java

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

...troller/devicemanager/internal/DeviceUniqueIndexTest.java

...t/floodlightcontroller/devicemanager/test/MockDevice.java

...lightcontroller/devicemanager/test/MockDeviceManager.java