After this patch nova rejects the add host to aggregate API action
if the host has instances and the new aggregate for the host would
mean that these instances need to move from one AZ (even from the
default one) to another. Such AZ change is not implemented in nova
and currently leads to stuck instances.
Similarly nova will reject remove host from aggregate API action if the
host has instances and the aggregate removal would mean that the
instances need to change AZ.
Depends-On: https://review.opendev.org/c/openstack/tempest/+/821732
Change-Id: I19c4c6d34aa2cc1f32d81e8c1a52762fa3a18580
Closes-Bug: #1907775
3c0eadae0b