packaging: engine-setup - make firewall checking more robust
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 <3681fb3205baf680cd6a957dddfb09244e62ce7a@redhat.com>
Change-Id: If10096e8f9e1141d2c0a45b600b0e82e849b59ba

yingyun001/ovirt-engine,yapengsong/ovirt-engine,OpenUniversity/ovirt-engine,halober/ovirt-engine,halober/ovirt-engine,walteryang47/ovirt-engine,eayun/ovirt-engine,zerodengxinchao/ovirt-engine,eayun/ovirt-engine,zerodengxinchao/ovirt-engine,halober/ovirt-engine,yapengsong/ovirt-engine,eayun/ovirt-engine,zerodengxinchao/ovirt-engine,zerodengxinchao/ovirt-engine,yingyun001/ovirt-engine,zerodengxinchao/ovirt-engine,yingyun001/ovirt-engine,OpenUniversity/ovirt-engine,yapengsong/ovirt-engine,walteryang47/ovirt-engine,halober/ovirt-engine,walteryang47/ovirt-engine,eayun/ovirt-engine,yingyun001/ovirt-engine,walteryang47/ovirt-engine,yingyun001/ovirt-engine,OpenUniversity/ovirt-engine,eayun/ovirt-engine,OpenUniversity/ovirt-engine,OpenUniversity/ovirt-engine,yapengsong/ovirt-engine,yapengsong/ovirt-engine,walteryang47/ovirt-engine