luci-app-upnp: Fix rpc handler for nftables

[kode54]

Rewrite great portions of the rpcd handler script to utilize the newer nftables implementation for firewall4-using versions. This is required because miniupnpd-nftables creates tables that are incompatible with iptables-nft. There may be some race conditions with deleting the lease entries, since it opens the file to locate the line number to delete. There could be a better way to do this.

Signed-off-by: Christopher Snowhill [email protected]

[hnyman]

I wonder if we would need separate luci-app-upnp-iptables and luci-app-upnp-nftables, as miniupnpd has both variants (and there are die-hard fw3 users)

Any thoughts, @jow- ?

[jow-]

Superseded by 82eec98944714c2b61f6e54291bc8f22983bb122