test_003_create_networks flakey failure

[Christopher Yeoh]

Get spurious failures in test_003_create_networks ocassionally:

ft56.3: tempest.scenario.test_network_basic_ops.TestNetworkBasicOps.test_003_create_networks[gate,smoke]_StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

Traceback (most recent call last):
  File "tempest/scenario/test_network_basic_ops.py", line 174, in test_003_create_networks
    router = self._get_router(self.tenant_id)
  File "tempest/scenario/test_network_basic_ops.py", line 139, in _get_router
    router.add_gateway(network_id)
  File "tempest/api/network/common.py", line 78, in add_gateway
    self.client.add_gateway_router(self.id, body=body)
  File "/opt/stack/new/python-neutronclient/neutronclient/v2_0/client.py", line 108, in with_params
    ret = self.function(instance, *args, **kwargs)
  File "/opt/stack/new/python-neutronclient/neutronclient/v2_0/client.py", line 416, in add_gateway_router
    body={'router': {'external_gateway_info': body}})
  File "/opt/stack/new/python-neutronclient/neutronclient/v2_0/client.py", line 1192, in put
    headers=headers, params=params)
  File "/opt/stack/new/python-neutronclient/neutronclient/v2_0/client.py", line 1175, in retry_request
    raise exceptions.ConnectionFailed(reason=_("Maximum attempts reached"))
ConnectionFailed: Connection to neutron failed: Maximum attempts reached

http://logs.openstack.org/99/45199/1/check/gate-tempest-devstack-vm-neutron/dd6b557/testr_results.html.gz