netcmd: Extend 'backup restore' command to handle renamed domains

netcmd: Extend 'backup restore' command to handle renamed domains

When restoring a renamed domain backup, we need to register the new
realm's DNS zone. We do this in the restore step because we don't know
the new server's IP/hostname in the backup step.

Because we may have removed the old realm's DNS entries in the rename
step, the remove_dc() code may fail to find the expected DNS entries for
the DC's domain (the DCs' dnsHostname still maps to the old DNS realm).
We just needed to adjust remove_dns_references() as it was getting a
slightly different error code.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>