When users with the "can_change_status" permission try to edit the close message, a permission error occurs. This is because when checking for permission, users with no modify permission are all excluded. 

Code is changed to include the case of "can_change_status" permission.

Added test case to cover case where user with "can_change_status" permission but no modify permission should get permission error when trying to edit changenum; the case where user with "can_change_status" permission but no modify permission should get permission error when trying to add extra data; the case where user with "can_edit_reviewrequest" permission but no status mutation permission should get permission error when trying to modify status.

Manual testing and Review Board Unit Testing