Backends need to implement c/u/d_recordset

The current code means the central generate SOA/NS records are
not provisioned, nor or any records create via the V2 API.

Change-Id: I49dc3dda9d4b49305646a8b222165abaa3506959
Closes-Bug: 1366821
Closes-Bug: 1370621
Merge "Backends need to implement c/u/d_recordset"