samba-tool: add dns zoneoptions for aging control

samba-tool: add dns zoneoptions for aging control

This adds a subcommand for altering zone parameters.

At the moment the only options are related to record aging (a.k.a
scavenging). The code is structured to make it easy to add more
integer or boolean options, but it is not clear that this would be
useful; many other parameters are not used or would only have
deleterious effects.

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Wed Apr 21 10:04:14 UTC 2021 on sn-devel-184