hostname: do not use gethostbyname() for "hostname -s"

hostname: do not use gethostbyname() for "hostname -s"

There's no reason to call gethostbyname() on the value returned
by uname() when asked just for a short name of a host.  This may
also be wrong, when uname is set to one value, but in /etc/hosts
(or elsewhere) the "canonical" name is different.  This is often
the case for localhost entry in /etc/hosts:

  127.0.0.1     localhost       myname

With this content of /etc/hosts, and uname being set to myname,
busybox hostname -s will return localhost, while regular
hostname utility returns myname.

Fix this by not calling gethostbyname() for the simple
'hostname -s' use.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>