Integrate sd-notify policies into `kube play`. The policies can be
configured for all contianers via the `io.containers.sdnotify`
annotation or for indidivual containers via the
`io.containers.sdnotify/$name` annotation.
The `kube play` process will wait for all containers to be ready by
waiting for the individual `READY=1` messages which are received via
the `pkg/systemd/notifyproxy` proxy mechanism.
Also update the simple "container" sd-notify test as it did not fully
test the expected behavior which became obvious when adding the new
tests.
Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>
