I neglected to do this before.
Also, since these conf values now apply everywhere, shift the default
settings for these confs to just vgolan, where they are known-working.
As per openwrt.org[1], the `band` configurable was introduced in
OpenWrt 21.02.2, replacing `hwmode`.
To handle the pre-21.02.2 nodes to which we're deploying, allow us to
configure either of the two (but defaulting hwmode to null).
[1]: https://openwrt.org/docs/guide-user/network/wifi/basic
- Use empty 'ssid:' in your template when you want it to be removed but
the mesh_id added
- Add an stp network.device option so mesh loops don't break things
