reset chld_pid to 0 when acting upon a SIGCHLD so we don't try to send it

a kill then - tiny possible race there
pointed out by Brian Poole <raj@cerias.purdue.edu>

src/usr.sbin/ntpd/ntpd.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.c,v 1.21 2004/09/18 23:21:35 henning Exp $ */
+/*	$OpenBSD: ntpd.c,v 1.22 2004/09/23 01:53:07 henning Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -186,8 +186,10 @@ main(int argc, char *argv[])
 		}
 
 		if (sigchld) {
-			if (check_child(chld_pid, "child"))
+			if (check_child(chld_pid, "child")) {
 				quit = 1;
+				chld_pid = 0;
+			}
 			sigchld = 0;
 		}