Make the osquery instance status available in the knapsack

[RebeccaMahany]

The osquery runner should be able to report on the status of each of the instances it manages. Status should probably be one of unstarted|launching|healthy|unhealthy or similar. Since we are moving toward running multiple instances, status must be stored per-instance -- use the registration ID to store. (Currently we only have one "default" registration ID.)

We should add the instances' statuses to the status blob returned by localserver.