Comment 5 for bug 1974682

Let me re-summarize the situation.

So it was definitely the change[1] which introduced this test failure.

 [1] https://review.opendev.org/c/openstack/aodh/+/829870

This works with Gnocchi >=4.5 (which is not yet released) but breaks
compatibility with Gnocchi <=4.4 and to make it work with Gnocchi <=4.4,
we should ignore 400 as well as 404.

Currently unit/functional tests in aodh is pulling gnocchi from pypi so
the tests are using not master but 4.4.z which is the latest release,
and are hitting the issue.