(fixtures): Fix cloud module reference (need to be a symlink)

In order to run rspec tests on the current branch/patchset, cloud
module (in fixtures directory) need to be a symlink on the working
directory, otherwise the rspec test use master branch of cloud module.

Refs: #724
Merge pull request #727 from enovance/fixtures-symlink

(fixtures): Fix cloud module reference (need to be a symlink)
Advanced Firewalling feature

This patch enables Firewalling in this Puppet modules in a flexible way.

* Enable firewalling optionnaly (disabled by default).
* Enable 'pre' firewalling with defaults rules.
* Enable 'post' firewalling with DROP rule, with a debug option to
  disable it.
* Enable default rules for all services (OpenStack, etc).
* Ability to add custom firewall rules with Hiera
* Update puppetlabs-firewall refs
* Refactorize unit-tests