raw.lxc configs for maas-on-lxd may be incorrect minor number

[afreiberger]

https://docs.maas.io/2.6/en/installconfig-lxd-install

Under the example config, the major/minor device 10:237 may not be accurate for all kernels. I'm seeing 10:232. This should probably reference checking the maj:min numbers of /dev/kvm and adding that first cgroup.devices.allow rule to reflect the maj:min of /dev/kvm.

config:
raw.lxc: |-
lxc.cgroup.devices.allow = c 10:237 rwm
lxc.apparmor.profile = unconfined
lxc.cgroup.devices.allow = b 7:* rwm
security.privileged: "true"