subtests.docker_cli: Update documentation docstrings

This pull request updates documentation to the new layout. I left
configuration in where it was present to simplify moving the
configuration inot INI files later.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Merge pull request #350 from ldoktor/update_docs

subtests.docker_cli: Update documentation docstrings