Improve systemd / podman coupling
Implements the same strategy as outlined by the 'quadlet' project in https://github.com/containers/quadlet/blob/main/docs/ContainerSetup.md with respect to robust container shutdown.
Fixes ai3/prod#260
Implements the same strategy as outlined by the 'quadlet' project in https://github.com/containers/quadlet/blob/main/docs/ContainerSetup.md with respect to robust container shutdown.
Fixes ai3/prod#260