Fixed #3835 Delete MailBackup not working - Log shows a warning about SQL I...

Till Brehm

2016-04-20 86853d4d0fd66c277746e9e0cf07fbecbfbbc362

 install/sql/incremental/upd_0052.sql

New file
@@ -0,0 +1 @@
ALTER TABLE `client` ADD `default_slave_dnsserver` INT( 11 ) UNSIGNED NOT NULL DEFAULT '1' AFTER `limit_dns_zone`;