[CLEAN] res_config, res_users: cleaned call to imd.get_object() + code cleaning

[CLEAN] res_config, res_users: cleaned call to imd.get_object() + code cleaning
- res_config: raise by default, no need to set the argument at True
- res_users: directly embedded get_user_groups_view code inside update_user_groups_view.
The try / except is still necessary, because when installing a new db, groups and users
are created before the user_groups_view view effectively exist. Due to some circular
references, the try / except is therefore necessary to install a new db.

bzr revid: tde@openerp.com-20140116134056-nyiybx7zsr8rhkiv