Initialize the sa_flags member of an auto struct sigaction variable.

It contained whatever garbage happened to be on the stack.

PR:		bin/27457 (not confirmed yet, but almost certain)
MFC after:	1 day

usr.sbin/yppush/yppush_main.c

@@ -651,6 +651,7 @@ main(argc,argv)
 	sigaddset(&sa.sa_mask, SIGALRM);
 	sigaddset(&sa.sa_mask, SIGINT);
 	sa.sa_handler = async_handler;
+	sa.sa_flags = 0;
 
 	sigaction(SIGIO, &sa, NULL);