oo-accept-systems:  Fixes for obsolete and downloaded carts

Fix the `check_nodes_cartridges` test in `oo-accept-systems` to ignore obsolete cartridges returned by the node hosts, because the broker will not list obsolete cartridges, and to ignore downloaded cartridges returned by the by the broker, because a node will not have downloaded cartridges in its cartridge repository.
    
This commit fixes bug 1124938.

Modify the `check_nodes_cartridges` test in `oo-accept-systems` to warn about obsolete cartridges returned by the node hosts.