sh netstart, instead of using .

We don't want any of the variables created inside netstart to infect the
rc script.
ok claudio sthen aja

src/etc/rc

@@ -1,4 +1,4 @@
-#	$OpenBSD: rc,v 1.434 2014/07/14 10:10:44 ajacoutot Exp $
+#	$OpenBSD: rc,v 1.435 2014/07/17 15:08:29 deraadt Exp $
 
 # System startup script run by init on autoboot
 # or after single-user.
@@ -375,7 +375,7 @@ if [ X"${pf}" != X"NO" ]; then
 	fi
 	# bring up pfsync after the working ruleset has been loaded
 	if [ -f /etc/hostname.pfsync0 ]; then
-		. /etc/netstart pfsync0
+		sh /etc/netstart pfsync0
 	fi
 fi