Grenade job fails on tempest tests

Our voting gate job "gate-grenade-dsvm-manila" started failing on tempest tests run step with following error:

2016-08-08 12:49:21.305972 | Captured traceback:
2016-08-08 12:49:21.305985 | ~~~~~~~~~~~~~~~~~~~
2016-08-08 12:49:21.306003 | Traceback (most recent call last):
2016-08-08 12:49:21.306024 | File "tempest/test.py", line 273, in setUpClass
2016-08-08 12:49:21.306042 | six.reraise(etype, value, trace)
2016-08-08 12:49:21.306063 | File "tempest/test.py", line 261, in setUpClass
2016-08-08 12:49:21.306079 | cls.setup_credentials()
2016-08-08 12:49:21.306108 | File "tempest/api/compute/servers/test_create_server.py", line 35, in setup_credentials
2016-08-08 12:49:21.306130 | super(ServersTestJSON, cls).setup_credentials()
2016-08-08 12:49:21.306154 | File "tempest/api/compute/base.py", line 61, in setup_credentials
2016-08-08 12:49:21.306176 | super(BaseV2ComputeTest, cls).setup_credentials()
2016-08-08 12:49:21.306199 | File "tempest/test.py", line 361, in setup_credentials
2016-08-08 12:49:21.306218 | credential_type=credentials_type)
2016-08-08 12:49:21.306240 | File "tempest/test.py", line 535, in get_client_manager
2016-08-08 12:49:21.306263 | creds = getattr(cred_provider, credentials_method)()
2016-08-08 12:49:21.306289 | File "tempest/common/dynamic_creds.py", line 305, in get_primary_creds
2016-08-08 12:49:21.306308 | return self.get_credentials('primary')
2016-08-08 12:49:21.306333 | File "tempest/common/dynamic_creds.py", line 297, in get_credentials
2016-08-08 12:49:21.306349 | credentials.tenant_id)
2016-08-08 12:49:21.306376 | File "tempest/common/dynamic_creds.py", line 214, in _create_network_resources
2016-08-08 12:49:21.306399 | router = self._create_router(router_name, tenant_id)
2016-08-08 12:49:21.306428 | File "tempest/common/dynamic_creds.py", line 273, in _create_router
2016-08-08 12:49:21.306445 | tenant_id=tenant_id)
2016-08-08 12:49:21.306474 | File "tempest/lib/services/network/routers_client.py", line 26, in create_router
2016-08-08 12:49:21.306495 | return self.create_resource(uri, post_body)
2016-08-08 12:49:21.306521 | File "tempest/lib/services/network/base.py", line 60, in create_resource
2016-08-08 12:49:21.306542 | resp, body = self.post(req_uri, req_post_data)
2016-08-08 12:49:21.306565 | File "tempest/lib/common/rest_client.py", line 273, in post
2016-08-08 12:49:21.306591 | return self.request('POST', url, extra_headers, headers, body, chunked)
2016-08-08 12:49:21.306615 | File "tempest/lib/common/rest_client.py", line 667, in request
2016-08-08 12:49:21.306630 | resp, resp_body)
2016-08-08 12:49:21.306655 | File "tempest/lib/common/rest_client.py", line 770, in _error_checker
2016-08-08 12:49:21.306677 | raise exceptions.BadRequest(resp_body, resp=resp)
2016-08-08 12:49:21.306697 | tempest.lib.exceptions.BadRequest: Bad request
2016-08-08 12:49:21.306738 | Details: {u'message': u"Invalid input for external_gateway_info. Reason: '' is not a valid UUID.", u'type': u'HTTPBadRequest', u'detail': u''}

logs: http://logs.openstack.org/43/351843/3/check/gate-grenade-dsvm-manila/b37e035/console.html#_2016-08-08_12_49_21_304246

reason: neutron client call error here: http://logs.openstack.org/21/312321/7/check/gate-grenade-dsvm-manila/c303964/logs/grenade.sh.txt.gz#_2016-08-08_07_36_20_617