More config options for the linkstate monitor

[Vidar Faltinsen]

The linkstate monitor should have added flexibility. There are basically only two config options today;

1) All ports
2) All ports with topology

A third option that is of interest is

3) All router ports.

Typically router ports are stable, not like switch ports with end users directly connected. Further router ports will not have topology info in many instances, i.e. ports that are connected to external peers.

I believe the default config should be to monitor link state for all router ports (3) AND all ports with topology (2)