inetd: use snprintf() in inetd_setproctitle()

inetd_setproctitle() formats se_service (the service name taken verbatim
from inetd.conf) and the peer address into an 80-byte buffer with
sprintf(). A long service name can overflow it. Bound both calls with
snprintf().

MFC after:	1 week
Reviewed by:	markj
Differential Revision:	https://reviews.freebsd.org/D60879

usr.sbin/inetd/inetd.c

@@ -2094,9 +2094,9 @@ inetd_setproctitle(const char *a, int s)
 	if (getpeername(s, (struct sockaddr *)&ss, &size) == 0) {
 		getnameinfo((struct sockaddr *)&ss, size, pbuf, sizeof(pbuf),
 			    NULL, 0, NI_NUMERICHOST);
-		(void) sprintf(buf, "%s [%s]", a, pbuf);
+		(void) snprintf(buf, sizeof(buf), "%s [%s]", a, pbuf);
 	} else
-		(void) sprintf(buf, "%s", a);
+		(void) snprintf(buf, sizeof(buf), "%s", a);
 	setproctitle("%s", buf);
 }