Add libvirt-python to ceilometer hosts
Add libvirt-python to ceilometer hosts

Ceilometer utilizes the libvirt library for gathering
instance related metrics. This commit adds the package
to the ceilometer hosts.

Change-Id: I1e46a9a49b606e11cd12f06ce947990096b1ad08
Closes-Bug: #1522250

major/openstack-ansible,git-harry/os-ansible-deployment,mrda/openstack-ansible,open-switch/infra_openstack-ansible,git-harry/os-ansible-deployment,yanyao/openstack-ansible,yanyao/openstack-deployment-liberty,yanyao/newton,cfarquhar/openstack-ansible,BjoernT/openstack-ansible,mrda/openstack-ansible,yanyao/newton,Logan2211/openstack-ansible,yanyao/openstack-ansible,mancdaz/openstack-ansible,weezer/openstack-ansible,BjoernT/os-ansible-deployment,bunchc/openstack-ansible,BjoernT/os-ansible-deployment,open-switch/infra_openstack-ansible,mancdaz/openstack-ansible,git-harry/os-ansible-deployment,major/os-ansible-deployment,cloudnull/os-ansible-deployment,open-switch/infra_openstack-ansible,bunchc/openstack-ansible,stackforge/os-ansible-deployment,major/os-ansible-deployment,major/openstack-ansible,openstack/openstack-ansible,BjoernT/os-ansible-deployment,cfarquhar/openstack-ansible,robb-romans/openstack-ansible,mrda/openstack-ansible,stackforge/os-ansible-deployment,Logan2211/openstack-ansible,yanyao/openstack-deployment-liberty,yanyao/openstack-deployment-liberty,weezer/openstack-ansible,os-cloud/os-ansible-deployment,BjoernT/openstack-ansible,robb-romans/openstack-ansible,os-cloud/os-ansible-deployment,cloudnull/os-ansible-deployment,openstack/openstack-ansible