@tflidd i appreciate your answer here. You were totally right… i made the following change on mysql config
set-variable = max_allowed_packet=16M
upgrade completed successfully
2016-09-08T10:09:57+00:00 Repair step: Remove shares of a users root folder
2016-09-08T10:09:57+00:00 Starting code integrity check…
2016-09-08T10:10:26+00:00 Finished code integrity check
2016-09-08T10:10:26+00:00 Update successful
2016-09-08T10:10:26+00:00 Maintenance mode is kept active
2016-09-08T10:10:26+00:00 Reset log level
I turned off maintenance mode…
sudo /usr/bin/php /var/www/html/owncloud/occ maintenance:mode --off
but now i have http error 500 and owncloud is not working. Any more ideas?