[FIX] orm: inherited `active` fields should be used for the implicit filtering
[FIX] orm: inherited `active` fields should be used for the implicit filtering

This is for example used by hr.employee which
inherits from resource.resource, with the
`active` field located on the resource model.
Simplified some code too.

akretion/openerp-server,akretion/openerp-server,akretion/openerp-server