L2TPv3 VLAN Trunks

[lukego]

Extend Snabb NFV so that a VM can be connected to multiple L2TPv3 tunnel sessions. Each tunnel session will be mapped to a unique 802.1Q VLAN ID. (That is: The VM see VLAN tagged packets and Snabb Switch will map each VLAN into an L2TPv3 tunnel.)

• [ ] Extend the L2TPv3 app to support multiple VLAN-mapped tunnel sessions for one endpoint.
• [ ] Create unit tests (selftest function).
• [ ] Extend the snabbnfv configuration file to support this feature.
• [ ] Add CI functional test coverage (snabbnfv selftest.sh).
• [ ] Add the configuration to our Neutron API Extensions too.
• [ ] Extend snabbnfv packet filtering to apply to 802.1Q VLAN tagged packets. (This is not a part of the standard OpenStack Neutron API and may not be necessary.)