New resouce agent for the neutron-ha-tool

This resource agent wraps the Neutron HA Tool (neutron-ha-tool) that's
currently part of the openstack-network cookbooks for chef. It can be
used to check neutron for offline l3-agents that still have routers
assigend and migrate those routers to a different (online) l3-agent.
Merge pull request #17 from rhafer/neutron-ha-tool

New resouce agent for the neutron-ha-tool