"state" should be something else than "ok" then served-serial and commit-serial are not equal #419
Description
It's a NSD behavior follow-up on #417
nsd-control zonestatus reports zone state: ok even thought served-serial is several updates away from current commit-serial.
Example https://github.com/NLnetLabs/nsd/issues/417
Generally, perhaps it shouldn't be regarded as a fault state (since the new zone data is suppose to be installed, but currently hasn't been that yet).
So perhaps something like state: old-serial or similar would be an indication that the zone currently isn't on par with the latest zone NSD knows about.
This would make it much simpler to discover then the NSD updating process isn't working as expected (as per #417)