Move per-container forward rules to DOCKER chain

Closes #6034

Docker-DCO-1.1-Signed-off-by: Ian Bishop <ianbishop@pace7.com> (github: porjo)
as per [this comment](https://github.com/docker/docker/issues/6034#issuecomment-58492224), would be best here to not add any jump to ``DOCKER`` table if there is already any in ``FORWARD``