We were only using the Command field in specgen when determining
whether to enable systemd if systemd=true (the default) was used.
This does not include the entrypoint, and does not include any
entrypoint/command sourced from the image - so an image could be
running systemd and we'd not correctly detect this. Using the
full, final command resolves this and matches Podman v1.9.x
behavior.
Fixes#6920
Signed-off-by: Matthew Heon <matthew.heon@pm.me>
dc2ca45d75