Using a shared storage with threading model thread_specific causes crash

In 24.02 all Configuration objects were added to a collection, so that it would be possible to iterate over them at startup. That is completely unproblematic for all configuration objects that are created in MainWorker.

However, the Memcached and Redis cache storages create, when the threading model is thread_specific, configuration objects in the context of a routing worker and in parallell, which wreaks havoc as the book-keeping is not thread safe.