Bug 2071:  Check to see if we still have the switch in LLDPSpeaker

It can sometimes happen that we can loose our connection to a Node
Connector while we still have NodeConnectorUpdates to process.

When this happens, we will get a null md in LLDPSpeaker, and should
just drop the messages there.


Change-Id: Ie5810c5c00fbaeb7022f2496da7166edf109678d
Signed-off-by: Ed Warnicke <eaw@cisco.com>
Merge "Bug 2071:  Check to see if we still have the switch in LLDPSpeaker"