Make sure we don't try to .lower() system if it's None
Make sure we don't try to .lower() system if it's None

rackerlabs/openstack-guest-agents-unix,joejulian/openstack-guest-agents-unix,prometheanfire/openstack-guest-agents-unix,rackerlabs/openstack-guest-agents-unix,prometheanfire/openstack-guest-agents-unix,joejulian/openstack-guest-agents-unix,rackerlabs/openstack-guest-agents-unix,coreos/openstack-guest-agents-unix,coreos/openstack-guest-agents-unix,coreos/openstack-guest-agents-unix,coreos/openstack-guest-agents-unix,prometheanfire/openstack-guest-agents-unix,joejulian/openstack-guest-agents-unix