This is a subset of the changes for implementing the floating IP
port forwarding feature in neutron, using OVN as the backend.
This changeset adds functional tests in maintenance task to ensure
that floating ips as well as port forwarding are properly handled.
Depends-On: https://review.opendev.org/#/c/741303/
Change-Id: I0671ed8d73ca8c0e3ba4aded81f395e20957d598
Partially-implements: ovn/port_forwarding
Partial-Bug: #1877447