Only one cache cleaning is allowed run at a time
Use long to calculate a hard limitand fix the punctuation of log
messages
Debug delay
Handle also hard limit in DiskCleanUp
RestServlet only schedules clean up, but doesn't wait for it to complete
Run cleaning in background thread
Shorter debug delay
Show system statistics and admin web also for filebroker
Comment and fine-tune
Merge branch 'fileserver-clean-up'