Don't cache resolved hostnames forever #16412
Description
Today we use InetAddress to represent IP addresses. InetAddress handles the work of resolving hostnames from DNS and from the local hosts file.
With the security manager enabled, successful hostname lookups are cached forever to prevent spoofing attacks. I don't know if this behaviour was different before the security manager was enabled, but it seems unlikely given issues such as #10337 and #14441.
It would be a useful improvement to be able to specify unicast hosts as hostnames which are looked up from DNS or hosts, then if the IP addresses change and the node need to reconnect to the cluster, it can just do a fresh lookup to gather the current IPs. Similar logic would help the clients.
If we make this change, it should be configurable (otherwise we're introducing the chance for spoofing) and we should consider the impact on hostname verification of ssl certs.
Testing this change would be hard...