[FIX] models: inverse name_get and _compute_display_name

The name_get should not call _compute_display_name, _compute_display_name should call namge_get. The previous behaviour was not backward-compatible with the old api. All the models redefining name_get (still a lot) would not have impacted the result of display_name and we would have got different results for both methods.
Changing the calls to _compute_display_name to proper name_get.