Allow clients to set the "advertised address"

[bboreham]

Sometimes machines have multiple IP addresses, and the one you wish peers to connect to is not the same as the one you connect out on.

[montanaflynn]

I think this could be the cause of logs we're getting in a kubernetes cluster:

2021/08/05 11:52:21 [swarm] error during gossip (->[10.2.56.252:46358] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:28 [swarm] error during gossip (->[10.2.54.169:55488] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:35 [swarm] error during gossip (->[10.2.30.183:23222] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:38 [swarm] error during gossip (->[10.2.54.169:53340] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:41 [swarm] error during gossip (->[10.2.56.252:30724] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:42 [swarm] error during gossip (->[10.2.9.169:48067] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)
2021/08/05 11:52:42 [swarm] error during gossip (->[10.2.93.198:23956] connection shutting down due to error during handshake: failed to receive remote protocol header: EOF)