Use LLDP to get switch port mapping

Provides a function to listen for LLDP packets on the network.
Listens on one or all of the network interfaces, and then parses the found
packets.

Change-Id: I1545a41f46cd0916aab9c43ce036865454fa66e0
Co-Authored-By: Josh Gachnang <josh@pcsforeducation.com>