Fix attribute::delete proc so it leverages stored procedure capability of dropping the database table as well (was broken before)This is needed for a non-xotcl portable way of dropping acs_attributes
fix site-node test in regression testdon't use per-request caching, since we migh shoot in our own footinterrupt cache_transaction to achieve desired semanticsallow in a few cases empty node_ids for method "get_url" as it is used by current OpenACS
Port from downstream cache transaction logics and fix automated test as now db_transaction will return 0 instead of the empty string (and no particular return value should be assumed)
