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.

Change-Id: I1be793bb4ea938603f13b4e599edc72f83499d44
Signed-off-by: Ofer Schreiber <oschreib@redhat.com>
(cherry picked from commit 3a34cda66edd76d49af7905fcfeb218acbf35a50)