Add some additional unit tests and change error status to null from NONE.  Some minor serializer cleanup

Correct race condition in device learning and topology, remove deviceManager from listening linkEvent

This reverts commit 0ae432f4.

Conflicts:

	src/main/java/net/floodlightcontroller/devicemanager/internal/DeviceManagerImpl.java

Cleanup of topology manager to match floodlight style.  Remove StackTraceUtil.  Add packet-in listener to topology

This reverts commit 51ca40a3.

Conflicts:

	src/main/java/net/floodlightcontroller/devicemanager/internal/DeviceManagerImpl.java

Add 5 seconds for attachment point change from one broadcast domain to another.  When the attachment points flap quickly, the controller should avoid learing the attachment point but should continue processing the packet.

Device manager will have a 5-second time gap to change an attachment point for a host from one broadcast domain to another.

Fix a bug for checking BDDP packet if the packet is not unicast for it to continue down the processing chain.

If the incoming node port is blocked, allow only unicast and BDDP packets to continue down the processing chain.

When the device manager gets cleaned up (or when during topologyChanged), it should consider the time difference between switching from broadcast to non-broadcast attachment points (as they might be previously on two different switches).