syscall: fix openbsd sysctl hostname/domainname workaround
syscall: fix openbsd sysctl hostname/domainname workaround

Fixes issue 2509.

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/5451055

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go