FACT-694: ec2 facts doesnt work for kvm

The ec2 facter is restricted only for xen by matching
virtual fact to xen, because of this, ec2 facts doesn't
work for openstack with kvm hypervisor.

Fixed it by adding kvm also in the match.
Merge pull request #776 from hkumarmk/bugfix_fact-694

FACT-694: ec2 facts doesnt work for kvm