exclude incomplete LLDP results
better handling of multiple discovery protocols

The new algorithm is:
- start with LLDP
- complete with CDP:
 - for interface without known neighbor, just use CDP info
 - for interface with a known neighbor, check if the name match:
  - if it matches, assume it is the same neighbor, and complete LLDP info
  - if it doesn't, raise a warning, and delete LLDP info
- complete with EDP:
 - for interface without known neighbor, just use EDP info
 - for interface with a known neighbor, check if the name match:
  - if it matches, assume it is the same neighbor, and complete LLDP info
  - if it doesn't, raise a warning, and delete LLDP info