After patch [1] new RBAC policies changed in the way that SYSTEM_ADMIN
user isn't anymore allowed to e.g. create resources in behalf of some
projects. Now PROJECT_ADMIN needs to create such resources instead.
So this patch basically reverts most of the changes which were done
in [2] some time ago.
It also introduces new entry in the clouds.yaml file -
"devstack-admin-demo" which is "admin" user in the "demo" project as
it's needed to create some resouces in the demo project now.
Additionally, because of bug [3] this patch changes way how IPv6
external gateway IP is found using Neutron API. This change may be
reverted in the future when bug [3] will be fixed.
[1] https://review.opendev.org/c/openstack/neutron/+/821208
[2] https://review.opendev.org/c/openstack/devstack/+/797450
[3] https://bugs.launchpad.net/neutron/+bug/1959332
Depends-On: https://review.opendev.org/c/openstack/neutron/+/826828
Closes-Bug: #1959196
Change-Id: I32a6e8b9b59269a8699644b563657363425f7174
14a0c09001