This new section describes how the OVN L3 schedulers distribute
the ``Chassis`` candidate list among the Available Zones, in
order to provide more resilience to the L3 HA: if the active
LRP binding fails, the next in the list will belong to another
AZ.
Related-Bug: #2030741
Change-Id: I20aaeefb33c424dc1a9c13f94f2912d0fa973166