Monitoring integration

[erikh]

The info package allows us to export some basic information about the health of the services. We can probably use this to define thresholds within the services themselves to take action based on how healthy they are; e.g. a volplugin who's failing a lot of mounts, or has an obnoxious number of goroutines, may choose to restart itself or refuse mounting new devices until serviced.

It should also be able to signal a REST endpoint with any health updates.