* Move task directory destroy logic from alloc_dir to task_dir
* Update errors to wrap error cause
* Use constants for file permissions
* Make multierror handling consistent.
* Make helpers for directory creation
* Move mount dir unlink to task_dir Unlink method
* Make constant for file mode 710
Co-authored-by: Tim Gross <tgross@hashicorp.com>
Co-authored-by: Michael Schurter <mschurter@hashicorp.com>