Bka sessions

Cleanup, fixes from investigation of situation where json requests were failing because dss was out of sessions.

• 10910490 webserver: automatically remove automatic sessions on trusted port
• 18a0f15a sessionManager: refactor mutex to recursive mutes
• 10fad176 webserver: remove dead argument in logDownloadHandler

https://trello.com/c/djII9OJX/134-stabilize-tests