9.0 unittests decorated with postinstall are run even if the module was not updated

[gurneyalex]

case at hand:

I have a module for a customer which changes the ACL for sale.order. It also has some unittests.

if I run odoo.py -i customer_module --stop-after-init && odoo.py -u customer_module --test-enable --stop-after-init the tests of sale which are decorated with postinstall are run too, even if the sale module is not updated. And of course they fail which breaks my CI.