etc/netstart: use colon separator instead of dot with chown

OK jung@, deraadt@, jmc@

src/etc/netstart

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: netstart,v 1.183 2017/05/07 09:40:15 rpe Exp $
+#	$OpenBSD: netstart,v 1.184 2017/05/28 08:07:33 awolk Exp $
 
 # Turn off Strict Bourne shell mode.
 set +o sh
@@ -99,7 +99,7 @@ ifstart() {
 	if [[ "${_stat[0]}${_stat[2]}${_stat[3]}" != *---00 ]]; then
 		echo "WARNING: $_file is insecure, fixing permissions"
 		chmod -LR o-rwx $_file
-		chown -LR root.wheel $_file
+		chown -LR root:wheel $_file
 	fi
 
 	# Check for ifconfig'able interface, except if -n option is specified.