In go-ipfs, it is possible to manually configure addresses to announce
or not announce to the swarm.
https://github.com/ipfs/go-ipfs/blob/master/docs/config.md#addressesannounce
This PR adds the same feature to Lotus. It can be configured from the [libp2p]
section of either the .lotus or .lotusstorage config.toml file. Example:
[Libp2p]
ListenAddresses = ["/ip4/0.0.0.0/tcp/34515", "/ip6/::/tcp/34515"]
AnnounceAddresses = ["/ip4/52.13.91.110/tcp/34515"]