Fix boolean that always returned true for selinux fact

Facter returns 'false' if selinux is not enabled.
Puppet evaluates it as true as it is not empty.

Change-Id: I2f1d9a348fd981292aeef177b57f08e1b7ef2732
Closes-bug: #1328547
(cherry picked from commit 6d35b1e8cf41a4c86b9aec7f9d7b5bced93cba7e)