Update to link discovery manager.  LLDPs are sent every one second; with a three second timeout on ports where links were already found.  On ports where links are not present, LLDPs are sent once in every 15 seconds.

Bug fix: handleLLDP() method uses incorrect port variable when getting the state of the packet-in port.

Cloning is currently implemented using serialize()/deserialize() which
isn't terribly efficient, but one an always revisit if performance
becomes an issue.

Bug fix: prevCluster assignment is changed to reflect the L2 domain ID of the prev entity.  It was possible for cur and prev to be swapped when duplicate attachment points were detected, where the prevCluster could have the wrong assignment.

Correct the set/get of TOS bits in OFMatch. The 6-bits of DSCP need to be top 6-bits of the network ToS byte.

Add a unit test that makes sure an exception is thrown when someone tries to remove a switch from the active switch map.

BSC-2116