iSCSI backend for Cinder volumes

As part of multi-backends, add iSCSI cinder backend.

* Add iscsi new backend.
* Allow to run iSCSI in multi-backend configurations via Hiera.
* Unit tests to validate both iSCSI & multi-backends.
NFS backend for Glance images

Bring support to mount filesystem_store_datadir to a remote NFS share.

Detailed description of this patch:
* add a new backend in cloud::image::api (nfs).
* add a new parameter to configure the NFS device (false by default).
* This parameter is required when using NFS backend, otherwise it will
  fail.
* Mount the NFS share using a new Puppet module by using a hash to
  configure the share.
* Add 4 new Puppet modules for NFS, common, types and rpcbind. The 3
  last ones are dependencies.
  Note: this NFS module has been chosen because it's well tested, quite
  updated and support Hiera data model which will allow us great
  flexibility for complex deployments.
* add unit tests with two new contexts when running NFS backend.
(gemfile) Relax rspec dependency and add bundler groups

This PR relax rspec dependency, for the moment we pin-point to a
specific version.
Merge pull request #637 from enovance/gemfile

(gemfile) Relax rspec dependency and add bundler groups
Merge pull request #633 from enovance/nfs-images

NFS backend for Glance images
NFS backend support to store Nova instances

Allow to store instances on a NFS share.

* New parameters: nfs_enabled, nfs_device and filesystem_store_datadir
* Disabled by default
* Unit tests with 3 contexts to validate all eventual cases
Merge pull request #634 from enovance/cinder-iscsi

iSCSI backend for Cinder volumes
Merge pull request #638 from enovance/instances-nfs

NFS backend support to store Nova instances
monitoring: Initial commit for sensu configuration

Install the sensu-puppet module and configure it
Merge pull request #560 from enovance/sensu

monitoring: Initial commit for sensu configuration
Puppetfile: fix missing comma
Merge pull request #642 from enovance/typo_puppetfile

Puppetfile: fix missing comma
lint: Unpin puppet-lint

puppet-lint 1.0.x has some nice features, including auto-fix, and other
things.
(gemfile) Unpin rspec version (upgrade to 3)
Convert specs to RSpec 2.99.2 syntax with Transpec

This conversion is done by Transpec 2.3.7
(lint) Fix a strange lint issue (indentation of => is not properly aligned)
Merge pull request #644 from enovance/qa-rspec

QA Rspec and puppet-lint
Update puppet-ceph to the last commit.

In order to use these changes:
https://github.com/enovance/puppet-ceph/commit/a9d9dacc464cfc7f8d157e71fef753894df08b1e
Update Puppetfile and .fixtures.yaml
cloud::database::sql wrong mariadb packages name

Change mariadb packages name on Redhat.
Fix puppet Package requirement on Redhat and Debian.

Signed-off-by: Dimitri Savineau <dimitri.savineau@enovance.com>
Merge pull request #643 from AlexandreNo/master

Update puppet-ceph to the last commit.