Changes in rules of session storage for visitors (04e97266) prevented the list
of viewed slides to be updated for public viewers, ending in possibly unlimited
counts. Fixed by touching the sessions, with a small performance improvement
"en passant".
See Odoo#86015
Task-2878900
closes odoo/odoo#93181
X-original-commit: 5b375d6c5e1f4a29add3976af7fd71600c7b4cda
Signed-off-by: Julien Castiaux <juc@odoo.com>