This is union Netdev plus a common member @peer-id, less the variant
members for NetClientDriver values 'nic' and 'hubport'.
Can 'type: 'nic' and 'type': 'hubport' occur?
No, it can't. We don't support NIC/hubport in query-netdevs, so we neither
create this
structure for them, nor store config.
Same for 'none', I guess.
As defined, NetdevInfo allows types 'none', 'nic', and 'hubport', it
just has no variant members for them. The fact that they can't occur is
not coded into the type, and therefore not visible in introspection.
To make introspection more precise, we'd have to define a new enum type.
How much that would complicate the C code is unclear.
Do we need it to be more precise? Eric, got an opinion?