Use '-s' Flag For USERHOST Segment

[Yankas]

Currently, the USERHOST segment uses the output of hostname. If called with no options, hostname will default to printing the fully qualified domain name (like hostname -f). The domain component is omitted (hostname -s) on Linux (GNU/Glibc?) systems.
A quick check on the FreeBSD manpage for hostname shows that it also defaults to using the -f flag.

I suggest using ('hostname -s') to unify the behavior across systems, since that i what most users would likely expect/want the segment to do. Another option would be to make the flag configurable, though I do not see much demand for an option to clutter the screen with the FQDN every time.