Multiple possible networks found error while running Tempest tests

Issue

• After Tempest completes testing it failed with the following error:

{5} tempest.api.compute.admin.test_delete_server.DeleteServersAdminTestJSON.test_admin_delete_servers_of_others [3.835841s] ... FAILED

Captured traceback:
~~~~~~~~~~~~~~~~~~~
    Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/tempest/api/compute/admin/test_delete_server.py", line 50, in test_admin_delete_servers_of_others
        server = self.create_test_server(wait_until='ACTIVE')
      File "/usr/lib/python2.7/site-packages/tempest/api/compute/base.py", line 200, in create_test_server
        **kwargs)
      File "/usr/lib/python2.7/site-packages/tempest/common/compute.py", line 197, in create_test_server
        **kwargs)
      File "/usr/lib/python2.7/site-packages/tempest/lib/services/compute/servers_client.py", line 89, in create_server
        resp, body = self.post('servers', post_body)
      File "/usr/lib/python2.7/site-packages/tempest/lib/common/rest_client.py", line 279, in post
        return self.request('POST', url, extra_headers, headers, body, chunked)
      File "/usr/lib/python2.7/site-packages/tempest/lib/services/compute/base_compute_client.py", line 48, in request
        method, url, extra_headers, headers, body, chunked)
      File "/usr/lib/python2.7/site-packages/tempest/lib/common/rest_client.py", line 668, in request
        self._error_checker(resp, resp_body)
      File "/usr/lib/python2.7/site-packages/tempest/lib/common/rest_client.py", line 789, in _error_checker
        raise exceptions.Conflict(resp_body, resp=resp)
    tempest.lib.exceptions.Conflict: Conflict with state of target resource
    Details: {u'message': u'Multiple possible networks found, use a Network ID to be more specific.', u'code': 409}