Comment 9 for bug 1852770

I'm able to see this issue on centos8 jobs.

tempest.scenario.test_network_v6.TestGettingAddress.test_slaac_from_os[compute,id-2c92df61-29f0-4eaa-bee3-7c65bef62a43,network,slow]
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Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "/usr/lib/python3.6/site-packages/tempest/common/utils/__init__.py", line 89, in wrapper
        return f(*func_args, **func_kwargs)
      File "/usr/lib/python3.6/site-packages/tempest/scenario/test_network_v6.py", line 244, in test_slaac_from_os
        self._prepare_and_test(address6_mode='slaac')
      File "/usr/lib/python3.6/site-packages/tempest/scenario/test_network_v6.py", line 193, in _prepare_and_test
        sshv4_1, ips_from_api_1, srv1 = self.prepare_server(networks=net_list)
      File "/usr/lib/python3.6/site-packages/tempest/scenario/test_network_v6.py", line 133, in prepare_server
        fip = self.create_floating_ip(thing=srv)
      File "/usr/lib/python3.6/site-packages/tempest/scenario/manager.py", line 1023, in create_floating_ip
        result = client.create_floatingip(**kwargs)
      File "/usr/lib/python3.6/site-packages/tempest/lib/services/network/floating_ips_client.py", line 30, in create_floatingip
        return self.create_resource(uri, post_data)
      File "/usr/lib/python3.6/site-packages/tempest/lib/services/network/base.py", line 61, in create_resource
        resp, body = self.post(req_uri, req_post_data)
      File "/usr/lib/python3.6/site-packages/tempest/lib/common/rest_client.py", line 283, in post
        return self.request('POST', url, extra_headers, headers, body, chunked)
      File "/usr/lib/python3.6/site-packages/tempest/lib/common/rest_client.py", line 687, in request
        self._error_checker(resp, resp_body)
      File "/usr/lib/python3.6/site-packages/tempest/lib/common/rest_client.py", line 808, in _error_checker
        raise exceptions.Conflict(resp_body, resp=resp)
    tempest.lib.exceptions.Conflict: Conflict with state of target resource
    Details: {'type': 'IpAddressGenerationFailure', 'message': 'No more IP addresses available on network 21d38e25-5f7d-464e-8c2c-dac3d20b8230.', 'detail': ''}

Job link: https://review.rdoproject.org/zuul/builds?job_name=periodic-tripleo-ci-centos-8-standalone-full-tempest-scenario-master