set socks auth for stream isolation
People are using the Tor that comes with TBB for other stuff than Tor Browser traffic (onionshare etc.).
As long as #3455 (moved) is not implemented, please consider setting a default (or random?) socks auth, unless the TOR_SOCKS_AUTH env variable is set.
Tor would notice it thanks to IsolateSOCKSAuth and all Tor Browser traffic would go through its own circuit.