Telemetry payload includes a JSON object enumerating devices with at least one backed-up config

That object is patterned after the existing nodesBySysoid item

• Each key is a nodesysoid

  • Except that if one or more nodes with backups do not have a nodesysoid, we want to capture that too – a key like none is used for this entry

• Each value indicates how many nodes with that sysObjectID (or lack thereof, for the case of none) have at least one config backup available

We're counting devices (nodes), not configs