arping: fix sent vs received packages return value

My earlier signalfd() and timerfd() work really messed up sent vs received
package counter comparison, and related command return value.  Basically
everything always mismatched, and that was expected with corner case of one
package only that did match and caused none-zero return.  Oh my, that is
pretty much as wrong the code could have been.

Reported-by: MarcusRoeckrath
Addresses: iputils#190
Broken-since: 67e070d
Signed-off-by: Sami Kerola <kerolasa@iki.fi>

arping.c

@@ -792,7 +792,7 @@ static int event_loop(struct run_state *ctl)
 	close(tfd);
 	freeifaddrs(ctl->ifa0);
 	rc |= finish(ctl);
-	rc |= !(ctl->brd_sent != ctl->received);
+	rc |= (ctl->sent != ctl->received);
 	return rc;
 }