Transport's publish address should report its hostname

[DaveCTurner]

There are situations in which the hostname of the transport's publish address is important. For instance, if node-to-node TLS is enabled including full certificate verification then it is the hostname of the node's publish address that we are verifying.

I suspect that #32729 was raised because we hide the hostname of the publish address. This log message was quoted as an example of the problem:

[2018-07-02T00:45:20,095][INFO ][o.e.t.TransportService   ] [data-0] publish_address {10.0.0.6:9300}, bound_addresses {10.0.0.6:9300}

However this does not indicate that the hostname is lost. We simply don't show it. The same is true in the output from GET _nodes:

...
  "transport": {
    "bound_address": [
      "127.0.0.1:9300"
    ],
    "publish_address": "127.0.0.1:9300",
    "profiles": {}
  },
...

Similar to #32806, I think we should expose the hostname in these addresses to clarify that it's still there and to aid troubleshooting when setting up full certificate verification.

[elasticmachine]

Pinging @elastic/es-distributed