Ensure kernel params are properly set on bridges

We set various things including UDP buffers for the openvpn hosts, but we should make sure we're doing it for bridges: https://0xacab.org/leap/container-platform/lilypad/-/blob/main/config/roles/openvpn/tasks/openvpn.yml?ref_type=heads#L49-58

kcptun has some suggested params as well: https://github.com/xtaci/kcptun?tab=readme-ov-file#quickstart