Install openstack-resource-agents from crowbar-pacemaker cookbook

It's not extremely clean to do openstack bits here, but it simplifies
many things. If this barclamp will be used for non-openstack setups too,
then we can actually have Crowbar orchestrate things to tell the
cookbook about which resource agents to install.
Merge pull request #41 from vuntz/openstack-ra

Install openstack-resource-agents from crowbar-pacemaker cookbook