nova-cpu: fix migration support

In Debian, libvirt service has now the same name as in Red Hat (libvirtd).
A patch has been done: https://review.openstack.org/#/c/128399/

This patch aims to update cloud::compute::hypervisor.
Update refs for puppet nfs module
Drop Puppet 3.2 support

This patch could be reverted later, but currently Travis does not pass
rspec tests with Puppet 3.2.

Minimum release expected is now Puppet 3.6.
Merge pull request #685 from enovance/update-nova-cpu

Fix Live-migration & NFS support for nova-compute