#2 Unused queue entries are not cleaned

[kwr]

There is incorrect logic to cleanup unused queue entries.

Such entries are created when:
1) A request is made for a client that is not available (wrong authentication code provided in request or client is not running).
2) The Browser App is closed (or page refreshed) before a response from the client is read (in case of file retrieval).
3) User cancels the request.