Mixes in napalm-device-types' HostFirewallMixin. The transport runs the shared
read-only command as root on an exec channel: nft prints the whole ruleset as
one line of JSON, longer than the PTY takes reliably, and both nft and
iptables-save need CAP_NET_ADMIN. Requires napalm-device-types 4.21.0;
version 0.13.0.