When a RoutingWorker is destructed, all existing local data will
unconditionally be destroyed.
The case in point is the vector<SFilterDef>s that are held as routing
worker local data by the Service. Unless the local data is deleted, the
filter defs will not be deleted at shutdown.
This is somewhat brute-force (but good to have in place nonetheless) as
the deletion of the local data should be done by the Service and before
the routing worker thread has exited.
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