test_dhcp_stateful_fixedips_duplicate and test_dhcp_stateful_fixedips works incorrect with Contrail SDN

[Mykola Yakovliev]

Tests

test_dhcp_stateful_fixedips_duplicate
test_dhcp_stateful_fixedips

relying on `random.randrange` when selecting IP from subnet `allocation_pool`.

It cause some problems with Contrail SDN. For internal usage, Contrail allocates `:1` and `:2` (as well as `.1` and `.2`), where `:1` acts as a gateway and `:2` acts as a DNS.

Since tests aren't expect anything on `:2`, when by pure random this IP got selected for test purpose - test fails.

``
Traceback (most recent call last):
  File "/home/rally/tempest/tempest/api/network/test_dhcp_ipv6.py", line 358, in test_dhcp_stateful_fixedips_duplicate
    'ip_address': ip}])
  File "/home/rally/tempest/tempest/api/network/base.py", line 161, in create_port
    **kwargs)
  File "/home/rally/tempest/tempest/lib/services/network/ports_client.py", line 28, in create_port
    return self.create_resource(uri, post_data)
  File "/home/rally/tempest/tempest/lib/services/network/base.py", line 61, in create_resource
    resp, body = self.post(req_uri, req_post_data)
  File "/home/rally/tempest/tempest/lib/common/rest_client.py", line 279, in post
    return self.request('POST', url, extra_headers, headers, body, chunked)
  File "/home/rally/tempest/tempest/lib/common/rest_client.py", line 675, in request
    self._error_checker(resp, resp_body)
  File "/home/rally/tempest/tempest/lib/common/rest_client.py", line 796, in _error_checker
    raise exceptions.Conflict(resp_body, resp=resp)
tempest.lib.exceptions.Conflict: Conflict with state of target resource
Details: {u'message': u'An unknown exception occurred.', u'type': u'Conflict', u'detail': u''}
``

The extra confusion here adds by the fact that test_dhcp_stateful_fixedips_duplicate actually tests conflict situation.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/614866

[Martin Kopec (mkopec)]

There is a comment in the related review asking to clarify a few things .. until then I'll move this to Incomplete state as this is a 2 year old bug and it might have got addressed already or not be relevant anymore.

[Martin Kopec (mkopec)]

Moving to Invalid due to inactivity, feel free to reopen this by providing more info as requested in the review.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Martin Kopec <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/tempest/+/614866
Reason: the associated bug is in Invalid state, feel free to reopen the bug and reactivate this change if still needed