elm genlist: Fixed _item_content_set_hook. Use _item_content_unset_hook internally.
elm genlist: Fixed _item_content_set_hook. Use _item_content_unset_hook internally.

SVN revision: 69742

FlorentRevest/Elementary,FlorentRevest/Elementary,rvandegrift/elementary,tasn/elementary,rvandegrift/elementary,FlorentRevest/Elementary,tasn/elementary,tasn/elementary,tasn/elementary,tasn/elementary,FlorentRevest/Elementary,rvandegrift/elementary,rvandegrift/elementary