Comment 7 for bug 1830763

In the case of test_from_dvr_to_dvr_ha, most of the occurrences failed while waiting for router ports down: https://github.com/openstack/neutron-tempest-plugin/blob/a7bb1619d43b413eb8d5849eb6df8d0dee260660/neutron_tempest_plugin/scenario/test_migration.py#L81

Here's the test traceback:

Traceback (most recent call last):
  File "/opt/stack/tempest/.tox/tempest/lib/python3.6/site-packages/neutron_tempest_plugin/scenario/test_migration.py", line 222, in test_from_dvr_to_dvr_ha
    after_dvr=True, after_ha=True)
  File "/opt/stack/tempest/.tox/tempest/lib/python3.6/site-packages/neutron_tempest_plugin/scenario/test_migration.py", line 136, in _test_migration
    self._wait_until_router_ports_down(router['id'])
  File "/opt/stack/tempest/.tox/tempest/lib/python3.6/site-packages/neutron_tempest_plugin/scenario/test_migration.py", line 81, in _wait_until_router_ports_down
    timeout=300, sleep=5)
  File "/opt/stack/tempest/.tox/tempest/lib/python3.6/site-packages/neutron_tempest_plugin/common/utils.py", line 83, in wait_until_true
    raise WaitTimeout("Timed out after %d seconds" % timeout)
neutron_tempest_plugin.common.utils.WaitTimeout: Timed out after 300 seconds