Neutron: Move tunnel and rate policing parameters into binding:profile

Move tunnel and rate policing parameters from binding:vif_details into binding:profile. On the Neutron side this means they can be modified at any time by the administrator.

Rate policing now has a dedicated `rx_police_gbps` parameter that can be enabled/adjusted on any port at any time. (This replaces the previous global choice of enforcing rate limiting or not.)