Glance: fix OSSA 2014-041

* Puppetfile: update refs of puppet-openstacklib & puppet-glance to have
  policy.json configuration feature.
* cloud::image::api: add a new param to configure policies with by
  default a policy to fix OSSA 2014-041.
* test with rspec the result.
Merge pull request #740 from enovance/protect-glance

Glance: fix OSSA 2014-041