packaging: engine-setup - make firewall checking more robust

1. Don't execute systemctl if it's not available in the system.
2. append ".service" to services name for backward compatibility.

Signed-off-by: Ofer Schreiber <oschreib@redhat.com>
Change-Id: If10096e8f9e1141d2c0a45b600b0e82e849b59ba