Trying to directly AXFR from dnsmasq is a mess, since their zone is
barely compliant with spec, it doesn't support notifies, and it is
generally really messy.
This implements an advanced "AXFR parser" system, which looks at the
results of an AXFR from the local dnsmasq instances per-network, and
updates the real replicated MariaDB pdns backend cluster with the
changed data. This allows a sensible, transferable zone with its own
SOA that is dynamically reconfigured as hosts come and go from the
dnsmasq zone.