support for both provide & self-service networks

Currently in neutron, supports either provider network or self-service network in one setup.

The proposal is to support both provider and self-service network in one single setup.
This can be implemented by having 3 interfaces in compute nodes, one for management network, the second one for provider network that supports one flat or multiple vlan provider networks and the third one for self-service network (overlay network - vxlan).

Through this, user can create multiple provider networks (through vlan - second interface) and multiple self-service networks (communicate through third interface - vxlan).