adt-run eats its log dir for breakfast

Before running any tests, adt-run does a 'rm -rf' of its log directory, and aborts if this causes any errors.

This is a problem because it's dangerous, it's unintuitive, and it breaks unix conventions.

Dangerous: Ever tried using $HOME as the log dir? When an attempt to use /tmp for logging fails due to permission issues, the next obvious choice is to use '.' or $HOME, which can cause disaster.

Unintuitive: The obvious first choices for a log dir are places like /tmp, ., $HOME, and /var/log. None of these actually work, and fail with a traceback. It's awkward to require a directory which doesn't even exist.

Breaks conventions: In general, most tools want to have a parent directory or an existing directory specified for their logging, as in the list of common directories above. Then the convention-compliant tool either writes logs to that directory (without first 'rm -rf'ing it) or creates a new child subdirectory such as /tmp/foo.24153/ to store results in. adt-run does not do this, which creates surprising results.

Could we change the log dir behavior of adt-run to be safer and more similar to other tools?