want disks, networking state in `omdb db instance show`

[hawkw]

The omdb db instance show command shows the current state of an instance record, along with its active VMM, migration target VMM, and active migration, if these exist. It does not currently provide any information on other resources that might be associated with the instance, such as its attached disks and external IPs.

It could be nice for the db instance show command to be a "one-so op shop" for everything associated with an instance's real We should consider having it track down disks attached to an instance and the instance's networking state and output them as well.