keystone: allow to change default_domain
keystone: allow to change default_domain

In keystone manifest, allow to change default domain id with a new
paramter.
That will be useful in puppet-keystone beaker tests, some tests are
using almost all keystone.pp code. With this patch, we'll be able to
re-use keystone.pp in beaker manifests.

Change-Id: Idd04ef48e867f5138bd9a2e04ea6f2fbc4369314

openstack/puppet-openstack-integration,openstack/puppet-openstack-integration,openstack/puppet-openstack-integration