Add all track_* options to JSON dump

[mayrstefan]

We are using JSON dumps to monitor keepalived. So far we can only see track_process in the v2 JSON.

Describe the solution you would like
We would like to see all track options to show up in the JSON dump. Currently track_file and vrrp_script are missing. Is there a technical reason this was not implemented?

Would the feature request be of benefit only to you, or is it more generally applicable?
This should help all monitoring systems gaining insight to the state of keepalived

Keepalived version
v2.3.4

[pqarmitage]

@mayrstefan It should be easy enough to add extra fields. Can you please provide a list of what fields you would like added to the JSON dump.

[mayrstefan]

At the end we want to use this information to feed it into our monitoring system. So the state is the most interesting thing to know. The next interesting field could be the current weight. So we can create a graph how it changes over time.