Add client recipe for compute

Add an explicit recipe for installing client
only packages.
Tests are also included.
Bumped minor version for this new feature.

Change-Id: Ie0c0abbd385baf4ba704867340f4ca19dc6529d1
Addresses: blueprint add-client-recipes
Make libvirt_images_type configurable

This setting allows changing the way libvirt stores ephemeral disk
images.  Possible settings are lvm, rbd, qcow2, raw and default.

When you pick "default", nova will use qcow2 when use_cow_images is
true. This cookbook does not handle that value, its default is true, so
default and qcow2 actually means the same thing here.  (There's no harm
done, I think.)

It includes additions to the README, specs and small cosmetic changes to
spec/nova-common_spec.rb.

Change-Id: If67029b1392f5657cde5da12702f757cb3c61805
Merge "Add client recipe for compute"
Merge "Make libvirt_images_type configurable"