Support running `podman play kube` in systemd by exploiting the
previously added "service containers". During `play kube`, a service
container is started before all the pods and containers, and is stopped
last. The service container communicates its conmon PID via sdnotify.
Add a new systemd template to dispatch such k8s workloads. The argument
of the template is the path to the k8s file. Note that the path must be
escaped for systemd not to bark:
Let's assume we have a `top.yaml` file in the home directory:
```
$ escaped=$(systemd-escape ~/top.yaml)
$ systemctl --user start podman-play-kube@$escaped.service
```
Closes: https://issues.redhat.com/browse/RUN-1287
Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>
8684d41e38