Use the expiry date to determine whether to replace the DB copy of

leapfile instead of using the leapfile serial number (create
timestamp).

PR:		209577
MFC after:	3 days

etc/rc.d/ntpd

@@ -108,8 +108,8 @@ ntpd_fetch_leapfile() {
 			$verbose fetching $url
 			fetch $ntp_leapfile_fetch_opts -o $ntp_tmp_leapfile $url && break
 		done
-		ntp_ver_no_tmp=$(get_ntp_leapfile_ver $ntp_tmp_leapfile)
-		if [ "$ntp_ver_no_tmp" -gt "$ntp_ver_no_db" ]; then
+		ntp_expiry_tmp=$(get_ntp_leapfile_expiry $ntp_tmp_leapfile)
+		if [ "$ntp_expiry_tmp" -gt "$ntp_leap_expiry" ]; then
 			$verbose using $url as $ntp_db_leapfile
 			mv $ntp_tmp_leapfile $ntp_db_leapfile
 		else