Neutron uses an AZ-unaware scheduler (LeastRoutersScheduler) by default
in its configuration and the neutron-api charm does not override it.
AZLeastRoutersScheduler inherits from LeastRoutersScheduler and does the
same, plus respects AZ hints when scheduling HA routers.
For --distributed --ha routers using AZLeastRoutersScheduler means that
snat namespaces will be scheduled with respect to the AZ hints specified
during router creation by an operator.
For --ha but not distributed routers using AZLeastRoutersScheduler means
that qrouter namespaces will be scheduled with respect to the AZ hints.
snat namespaces (--ha & --distributed) and qrouter namespaces (--ha
only) are placed by the scheduler to l3 agents that run in the dvr_snat
mode only so the scheduler change will affect both the deployments with
neutron-gateway units and the ones with neutron-openvswitch running with
use-dvr-snat=True.
Change-Id: I98cd67ff0cf5418a9699acc7aff96c3edb9b2341
Closes-Bug: #1886195
a155e9cf11