Allow setting the listen address for all Chutney hosts
In Tails' automated test suite we have plans to use Chutney to run a simulated Tor network (for increased performance and, in particular, robustness). Of course, we do not want to run that Chutney instance in the system under testing (i.e. the Tails instance) but on the host orchestrating the tests. In order to avoid having to forward traffic via firewall rules, we'd like it to be possible to make the Chutney hosts listen on some other IP address than localhost.
The attached patch allows setting the address all Chutney hosts will listen on via the
CHUTNEY_LISTEN_ADDRESS environment variable.