Neutron has changed to use ovs native interface by default, but when
the hypervisor is XenServer, we cannot use ovs native interface without
extra configurations in neutron-openvswitch-agent(q-agt) in compute
node.
This patch is to add the needed configurations automatically during
deployment, so user needn't to do it manually and restart q-agt.
Change-Id: Ibc69d3cdb4d75833f2ac16840c62bcacf460dd4f