Introduce LLDP facts

Use lldpctl's xml format to introduce a number of facts
 * lldppeer_ethX => the switch connected on that interface
 * lldpswport_ethX => the switchport description
 * lldpswport_id => The switchport id as reported by the switch
 * lldppeers => Comma separated list of all LLDP peers

where ethX is a given interface that both it and it's connected
counterpart speak LLDP

Change-Id: Icc744872f8dfed24eea149bc05766053cc2656a5