RFC: Add autotest directories to params

There are many places where we preppend autotest dirs to params. With this pull request we could set this directly in params as cartesian config supports variables `${variable}`.

As an example I picked few tests that are currently creating large files in `/tmp/` and replaced the `/tmp/` with `${autotest_tmp_dir}`.

I haven't successfully tested all the affected tests as some of them fails on my F18 or are in-executable (so the behavior remains unchanged).