There is no user for Slave Instances, so use super user instead.

New authentication ways allow to have multiple user with the same email.

Do not use modification date anymore, as it can not be trusted to check slapgrid access

Delivery lines with setup resource are required for security calculation.

Fetch partition directly from self, by using UnrestrictedMethod, and use later
_assertACI in order to check permission.

Rationale: unrestrictedSearchResults will return all partitions, when Software
Instance needs access to only one.

Also change behavior to ignore cases defined in e93f690.

1/ Partition without SR is ignored.
2/ Partition that are empty and already in destroyed state are ignored.

Access Contents Information is checked in order to avoid accessing unauthorised
objects.

This reverts commit c5409c67.

If it works well, all dead code will be cleaned in future versions of slapos.core