var-naming[no-role-prefix] should have a notion of internal variable

[rpelisse]

While it make sense to have any vars declare in defaults or a vars of role to be prefixed by the rolename, it seems strange to have to do so for internal variable, belonging to one play inside the role. The perfect example for that is the loop_var name. If a play inside a role iterate on some list, should this "one-time", internal variable be prefixed by the role name?