Have an option to disable the LRUFileCache

When using an S3 binary store, blobs are download to a LRUFileCache.

The LRUFileCache scans every 5s its entries to do the cleaning depending on total size or age.

For heavy processing we need to configure very big cache and this cleaning procedure has a high cost and is too frequent.

So we should have a way to change the cleaning frequency or to disable it if the cleaning is managed outside of Nuxeo.