Nest: Update handling of temporary attributes
The temporary atttributes are no longer removed by ea_do_prune(), but they are undefined by store_tmp_attrs() protocol hooks. This fixes several bugs where temporary attributes were removed when they should not or not removed when they should be. The flag EAF_TEMP is no longer needed and was removed. Update all protocol make_tmp_attrs() / store_tmp_attrs() hooks to use helper functions and to handle unset attributes properly. Also fix some related bugs like improper handling of empty eattr list.