Update Kademlia NetworkBehaviour in Rust Peer

[maschad]

Note that adding the Kademlia NetworkBehaviour in itself is not quite enough. You would (a) need to execute the bootstrap method regularly and (b) actively add peers (like you do, commented out, for the bootstrap nodes).

You can find an example here:

(a) https://github.com/mxinden/rust-libp2p-server/blob/4d887c720bf25ad282c58d8f7d9773715a2b5c70/src/main.rs#L162-L169

(b) https://github.com/mxinden/rust-libp2p-server/blob/4d887c720bf25ad282c58d8f7d9773715a2b5c70/src/main.rs#L172-L199

The latter will be automated once we have libp2p/rust-libp2p#2680.

Originally posted by @mxinden in #17 (comment)