[IMP] gamification_sale_crm: change date filed for definition "Logged Calls"

The field date_close is only computed when writing the state done. In v8, the phonecalls are always created in state done if the user is not in the group crm.group_scheduled_calls (displays menus to schedule calls.
As the field date_closed is then almost never set, change the date field by the one displayed in the form view. opw 614893
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64