Code review comment for ~mpontillo/maas:ha-dns-servers--bug-1753493

FWIW, this is the output of a deployed machine. The rackd.conf:maas_url: http://10.90.90.2:5240/MAAS

That tells the machines being deployed that;

1. The region is in 90.2
2. The metadata server is in 90.2
3. The proxy is in 90.2
4. The DNS server is in 90.2

As such, it doesn't matter if this IP is routed, on same subnet, a VIP or whatever. MAAS needs to be smart about this, because:

1. Machine facing rack controllers know where the region is (10.2).
2. MAAS knows the network model, and can determine that there's regions on the same subnet (10.1, 10.3)

Based on your changes, there's a lot of inconsistencies here provided that everything but DNS is correct (note that NTP is a different story, because NTP is based on rack connections).

ubuntu@pod-node01:/etc$ grep -sr 10.90.90. *
apt/apt.conf.d/90curtin-aptproxy:Acquire::http::Proxy "http://10.90.90.2:8000/";
cloud/cloud.cfg.d/90_dpkg_local_cloud_config.cfg: proxy: http://10.90.90.2:8000/
cloud/cloud.cfg.d/90_dpkg_local_cloud_config.cfg:apt_proxy: http://10.90.90.2:8000/
cloud/cloud.cfg.d/90_dpkg_local_cloud_config.cfg: maas: {consumer_key: vxJUs6nQy7SZ4rfsdy, endpoint: 'http://10.90.90.2:5240/MAAS/metadata/status/r73ym7',
cloud/cloud.cfg.d/50-curtin-networking.cfg: - address: 10.90.90.189/24
cloud/cloud.cfg.d/50-curtin-networking.cfg: gateway: 10.90.90.1
cloud/cloud.cfg.d/50-curtin-networking.cfg: - 10.90.90.3
cloud/cloud.cfg.d/50-curtin-networking.cfg: - 10.90.90.1
network/interfaces.d/50-cloud-init.cfg: dns-nameservers 10.90.90.3 10.90.90.1
network/interfaces.d/50-cloud-init.cfg: address 10.90.90.189/24
network/interfaces.d/50-cloud-init.cfg: gateway 10.90.90.1
ntp.conf:server 10.90.90.1 iburst
ntp.conf:server 10.90.90.3 iburst
resolv.conf:nameserver 10.90.90.3
resolv.conf:nameserver 10.90.90.1