[swarm 10.0] tests on network templates failed with http400

Detailed bug description:
Found on ci:
https://product-ci.infra.mirantis.net/job/10.0.system_test.ubuntu.network_templates/144/testReport/junit/(root)/deploy_cinder_net_tmpl/deploy_cinder_net_tmpl/
https://product-ci.infra.mirantis.net/job/10.0.system_test.ubuntu.network_templates/144/testReport/junit/(root)/deploy_ceph_net_tmpl/deploy_ceph_net_tmpl/
Steps to reproduce (cinder):
1. Revert snapshot with 3 slaves
2. Create cluster (HA) with Neutron VLAN/VXLAN/GRE
3. Add 1 controller + cinder nodes
4. Add 2 compute + cinder nodes
5. Upload 'cinder' network template'
6. Create custom network groups basing
     on template endpoints assignments
7. Run network verification
8. Deploy cluster
9. Run network verification
10. Run health checks (OSTF)
11. Check L3 network configuration on slaves
12. Check that services are listening on their networks only

Expected results:
Tests passed
Actual result:
Stack trace:
...
  File "/home/jenkins/workspace/10.0.system_test.ubuntu.network_templates/fuelweb_test/tests/test_net_templates_base.py", line 123, in create_custom_networks
    self.fuel_web.client.add_network_group(custom_net)
  File "/home/jenkins/workspace/10.0.system_test.ubuntu.network_templates/core/helpers/log_helpers.py", line 204, in wrapped
    result = func(*args, **kwargs)
  File "/home/jenkins/workspace/10.0.system_test.ubuntu.network_templates/fuelweb_test/models/nailgun_client.py", line 563, in add_network_group
    return self._post(url='/networks/', json=network_data).json()
  File "/home/jenkins/workspace/10.0.system_test.ubuntu.network_templates/fuelweb_test/models/nailgun_client.py", line 56, in _post
    return self.session.post(url=url, connect_retries=1, **kwargs)
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/keystoneauth1/session.py", line 675, in post
    return self.request(url, 'POST', **kwargs)
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/positional/__init__.py", line 101, in inner
    return wrapped(*args, **kwargs)
  File "/home/jenkins/venv-nailgun-tests-2.9/local/lib/python2.7/site-packages/keystoneauth1/session.py", line 570, in request
    raise exceptions.from_response(resp, method, url)
BadRequest: Bad Request (HTTP 400)

in api.log:
2016-10-10 11:08:39.084 DEBUG [7f790c203880] (logger) Request POST /api/networks/ from 10.109.7.1:47386 {"name": "mongo", "meta": {"ip_range": ["10.200.255.1", "10.200.255.254"], "unmovable": false, "use_gateway": false, "notation": "ip_ranges", "render_addr_mask": null, "render_type": null, "map_priority": 0, "configurable": true}, "interface": "br-mongo", "cidr": "10.200.255.0/24", "group_id": 1, "gateway": null}
2016-10-10 11:08:39.128 DEBUG [7f790c203880] (logger) Response code '400 Bad Request' for POST /api/networks/ from 10.109.7.1:47386

When I've tried to run POST request maunually with data {"name": "mongo", "meta": {"ip_range": ["10.200.255.1", "10.200.255.254"], "unmovable": false, "use_gateway": false, "notation": "ip_ranges", "render_addr_mask": null, "render_type": null, "map_priority": 0, "configurable": true}, "interface": "br-mongo", "cidr": "10.200.255.0/24", "group_id": 1, "gateway": null} I've got Bad request message with point "Additional properties are not allowed" for 'interface' key. When request does not contain <"interface": "br-mongo">, it does not initiate http 400 error.
Unfortunately, env is unavailable for reverting now.