Collect monitoring metrics from libbeat

[jalvz]

We have access to them already, we only need to index it.

[graphaelli]

#169 reminded me, is this done then?

[jalvz]

No - we have access to the data (and Andrew wrapped it up recently), but we are not indexing, so it's not in the dashboards, etc. Maybe it could be interesting to see pipeline acks/failures/etc, but we can also just close this if you don't think is worth it