1. Deprecate netlink over TCP
2. The remote netlink server works via 2 files (pipes)
3. Affected: NetNS

From now on it is possible to communicate with the remote
netlink via 2 file channels, like stdin/stdout.

Files must support the basic file API — read/write/close/flush.

The `Server()` routine takes 2 files wrapped in the `Transport`
protocol (see NetNS implementation).