testnet: rockylinux management ip addresses increment on reboot

[nihr43]

The lxdbr0-facing interfaces are all having their ips incremented by one when ansible reboots them.
Usually LXD's dhcp server is good about keeping these static - this isn't a problem with debian or ubuntu images.

This is LXD 5.19 on NixOS.

python3 testnet --clean --create --image rockylinux/9

+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-3019e  | RUNNING | 10.64.212.33 (eth0)  | fd42:334b:7451:a6cb:216:3eff:fe3f:632f (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-3100c  | RUNNING | 10.64.212.238 (eth0) | fd42:334b:7451:a6cb:216:3eff:fedb:c271 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-cf802  | RUNNING | 10.64.212.142 (eth0) | fd42:334b:7451:a6cb:216:3eff:fe8e:3924 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-spine-1b641 | RUNNING | 10.64.212.154 (eth0) | fd42:334b:7451:a6cb:216:3eff:febc:52b (eth0)  | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-spine-b9152 | RUNNING | 10.64.212.134 (eth0) | fd42:334b:7451:a6cb:216:3eff:feda:ec40 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+

+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-3019e  | RUNNING | 10.64.212.34 (eth0)  | fd42:334b:7451:a6cb:216:3eff:fe3f:632f (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-3100c  | RUNNING | 10.64.212.239 (eth0) | fd42:334b:7451:a6cb:216:3eff:fedb:c271 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-leaf-cf802  | RUNNING | 10.64.212.143 (eth0) | fd42:334b:7451:a6cb:216:3eff:fe8e:3924 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-spine-1b641 | RUNNING | 10.64.212.155 (eth0) | fd42:334b:7451:a6cb:216:3eff:febc:52b (eth0)  | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
| bgp-spine-b9152 | RUNNING | 10.64.212.135 (eth0) | fd42:334b:7451:a6cb:216:3eff:feda:ec40 (eth0) | CONTAINER       | 0         |
+-----------------+---------+----------------------+-----------------------------------------------+-----------------+-----------+