it seems, we can reactivate per-request caching for sitenodes, otherwise we see up to 37 locks per requests on get_node_id on openacs.org (regression test works fine)
fix site-node test in regression test don't use per-request caching, since we migh shoot in our own foot interrupt cache_transaction to achieve desired semantics allow in a few cases empty node_ids for method "get_url" as it is used by current OpenACS