Lowercase 'usage' and group -n with interface in it.

From jmc@, ok tb@

src/etc/netstart

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: netstart,v 1.195 2018/02/21 19:57:21 rpe Exp $
+#	$OpenBSD: netstart,v 1.196 2018/03/03 07:34:19 landry Exp $
 
 # Turn off Strict Bourne shell mode.
 set +o sh
@@ -200,7 +200,7 @@ FUNCS_ONLY=1 . /etc/rc.d/rc.subr
 _rc_parse_conf
 
 PRINT_ONLY=false
-USAGE="USAGE: ${0##*/} [-n] [interface ...]"
+USAGE="usage: ${0##*/} [[-n] interface ...]"
 V4_DHCPCONF=false
 V6_AUTOCONF=false