Documentation: update FAQ with entry about changing peer advertising
Been seeing this somewhat frequently.
`advertise-urls` specifies the addresses etcd clients or other etcd members should use to contact the etcd server. The advertise addresses must be reachable from the remote machines. Do not advertise addresses like `localhost` or `0.0.0.0` for a production setup since these addresses are unreachable from remote machines.
+#### Why doesn't changing `--listen-peer-urls` or `--initial-advertise-peer-urls` update the advertised peer URLs in `etcdctl member list`?
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+A member's advertised peer URLs come from `--initial-advertise-peer-urls` on initial cluster boot. Changing the listen peer URLs or the initial advertise peers after booting the member won't affect the exported advertise peer URLs since changes must go through quorum to avoid membership configuration split brain. Use `etcdctl member update` to update a member's peer URLs.
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### Deployment
#### System requirements
