UI content listings result in uncached calls for unpublished content

When listing the children of a content node in the UI (e.g. expanding the tree node), the UI usually performs well. However, if the node contains unpublished items this action could introduce a noticeable delay (a considerable delay if there are many such items). It turns out that for unpublished items there will be an uncached call to the content repository (and on to the DB) for each unpublished item.