Add ability to configure control_exchange

Add control_exchange parameter with default to 'openstack'.

The control_exchange configuration defaults to 'openstack' in Cinder.

Fixes: bug #1220272
Change-Id: Ic15e471a745568e5183ad9eedba92c213026309e
(cherry picked from commit 15e32b1e4ab513fbe980e84d6585be42385c0ca7)
Creates an empty init script override file if necessary

Without this patch, puppet runs were failing with the following error:

(/Stage[main]/Cinder::Volume::Rbd/File_line[set initscript env]) Could not
evaluate: No such file or directory - /etc/init/cinder-volume.override

Change-Id: Ibf42b4b09441c8a044f50af62246be31fe584e1b
Pin to posgresql 2.5 module

- Later version breaks backward compatibility
- Sort fixtures for better maintainability

Change-Id: I4197041025f5d89a02c83bfee20ef2f2788f756f
(cherry picked from commit 0ee4be96653b3d88bd2fea33e24453744d96f11a)
Prepping module for 2.2.0 release.

Updated Modulefile to version 2.2.0. Updated README.md with
latest release notes.

Change-Id: I9aab1c3ff9b5f801dd496c4947cba81fe4f879ac
(cherry picked from commit 4100e958fdecebe6eb486c8a09ba6954bcae5d71)
Merge branch 'grizzly' of https://github.com/gwdg/puppetlabs-cinder into grizzly