os: disable Hostname test on OpenBSD

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4901054

src/pkg/os/os_test.go

@@ -920,6 +920,12 @@ func TestHostname(t *testing.T) {
 	if syscall.OS == "windows" || syscall.OS == "plan9" {
 		return
 	}
+
+	// TODO(jsing): Fix nametomib() on OpenBSD
+	if syscall.OS == "openbsd" {
+		return
+	}
+
 	// Check internal Hostname() against the output of /bin/hostname.
 	// Allow that the internal Hostname returns a Fully Qualified Domain Name
 	// and the /bin/hostname only returns the first component