1. Remove the restriction of vxlan on yaml file
2. Configure iptables in Dom0 to enable vxlan port 4789
3. Move br-mesh from compute node to Dom0
4. Add mos-vxlan.service to take use of systemctl and make
sure when XenServer host reboot, the br-mesh and related
configurations is still there
5. Persist iptables rules
6. Add cleanup of br-mesh if it exist in in Dom0 when the
neutron network type is not vxlan
Change-Id: I1ab8ca56714167a2e20513b0f9b0ed4a82d9648e