TestNeutronVifPortIDMixin fails ... sometimes

ft1.7: ironic.tests.unit.drivers.modules.network.test_common.TestNeutronVifPortIDMixin.test_port_changed_client_idtesttools.testresult.real._StringException: Traceback (most recent call last):
  File "/usr/lib/python3.9/unittest/mock.py", line 1337, in patched
    return func(*newargs, **newkeywargs)
  File "/home/zuul/src/opendev.org/openstack/ironic/ironic/tests/unit/drivers/modules/network/test_common.py", line 1073, in test_port_changed_client_id
    dhcp_update_mock.assert_called_once_with(
  File "/usr/lib/python3.9/unittest/mock.py", line 208, in assert_called_once_with
    return mock.assert_called_once_with(*args, **kwargs)
  File "/usr/lib/python3.9/unittest/mock.py", line 918, in assert_called_once_with
    raise AssertionError(msg)
AssertionError: Expected 'update_port_dhcp_opts' to be called once. Called 0 times.

Happens in CI some small % of the time? Probably 10% or less. We should fix or disable it.