We can't really do a delete test here. Linux cgroups
implementation provides additional semantics - the cgroup cannot be
deleted if there are any tasks still running in the cgroup even if
the user attempting the delete has the file permissions to do so - we
cannot simulate that here. Even if we create a dummy 'tasks' file, we
wouldn't be able to simulate the delete behavior we need, since a cgroup
can be deleted using using 'rmdir' if the tasks file is empty. Such a
delete is not possible with a regular non-empty directory.