Fix OPENDJ-363: Make it more obvious in the setup tool that the fully-qualified hostname is critical for all secured connections

* improved heuristic for determining a default fully qualified host name. Reverse DNS lookups timeout after 1 second in order to avoid long delays if DNS is broken
* changed usage for host name which makes it clearer that the host name is required regardless of LDAPS/StartTLS configuration
* changed interactive CLI so that it always prompts for the fully qualified hostname
* changed the setup tool to make it clearer that it is prompting for the fully qualified hostname.

Tested on laptop with DNS and VM without DNS.