Use a variable for readability

MFC after:	3 days
X-MFC-to:	stable/10

usr.sbin/bsdinstall/scripts/wlanconfig

@@ -1,7 +1,7 @@
 #!/bin/sh
 #-
 # Copyright (c) 2011 Nathan Whitehorn
-# Copyright (c) 2013 Devin Teske
+# Copyright (c) 2013-2015 Devin Teske
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -168,7 +168,7 @@ if [ "$BSDINSTALL_CONFIGCURRENT" ]; then
 	f_dprintf "%s" "$output"
 fi
 
-exit 0
+exit $SUCCESS
 
 ################################################################################
 # END