[FIX] test_mail: fix timezone issue in activity test
[FIX] test_mail: fix timezone issue in activity test

Due to timezone difference between two test users the state of activities
depend on the time when the test is running. Indeed if user 1 plans an
activity for tomorrow this could already be today for user 2. Test
that ensure tomorrow is correctly computed should therefore be done with
users being in the same timezone. Current behavior is correct as activities
manipulate date that cannot always be timezoned back to another timezone.

How to reproduce the issue before this fix: run the activity mixin tests
between 0:00 and 1:00 in +1 TZ (Brussels).

ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo,ygol/odoo