P898427 Get holdings_xml.retrieve to flesh URIs properly

P898427 Get holdings_xml.retrieve to flesh URIs properly

Flesh URIs when requested with the -uris or -full feed type.
This was broken when commit f2b822f8 fixed authority browsing.

holdings_xml-full never appeared to retrieve URIs properly, so that has
been added.

This also makes holdings_xml-uris behave in the new manner of URIs as per
git commit ba47ecc61, retrieving URIs for ancestors rather than descendants.

Signed-off-by: James Fournie <jfournie@sitka.bclibraries.ca>
Signed-off-by: Dan Scott <dscott@laurentian.ca>