"Could not setup the environment of the managed proxy" when using init script

tor needs to pass the values of the environment variables PATH and HOME to the managed proxy. If it can't find those variables in its environment, it will fail with:

[warn] Could not setup the environment of the managed proxy at '/usr/local/bin/obfsproxy'.

People have encountered this, when they tried to use managed proxies with an init. script, and they init. script didn't set up those two variables before spawning tor.

We should work around this.