list servers always returns all with 'ip6' filter

A tempest test was failing because it was trying to filter servers based on ip from an ipv6 subnet but was not using the 'ip6' query param. But the fix to use 'ip6' failed because all servers are returned instead of just the one with that ipv6 addr.

This is most easily seen by just doing:

nova list --ip6 xxx

which returns all servers vs

nova list --ip xxx

which returns none.

For reference, the actual failing call from http://logs.openstack.org/98/179398/1/experimental/check-tempest-dsvm-neutron-full-non-admin/aa764bb/console.html:

2015-05-01 15:53:56.426 | 2015-05-01 15:22:28,839 30116 INFO [tempest_lib.common.rest_client] Request (ListServerFiltersTestJSON:test_list_servers_filtered_by_ip): 200 GET http://127.0.0.1:8774/v2/40784510a9f046a0a0d70f339f2d71d8/servers?ip6=fd81%3Aaad7%3Afb2%3A0%3Af816%3A3eff%3Afef3%3A8aaa 0.060s
2015-05-01 15:53:56.426 | 2015-05-01 15:22:28,840 30116 DEBUG [tempest_lib.common.rest_client] Request - Headers: {'X-Auth-Token': '<omitted>', 'Accept': 'application/json', 'Content-Type': 'application/json'}
2015-05-01 15:53:56.426 | Body: None
2015-05-01 15:53:56.426 | Response - Headers: {'content-type': 'application/json', 'x-compute-request-id': 'req-ac54be26-7689-4092-b42a-f3161c80295b', 'date': 'Fri, 01 May 2015 15:22:28 GMT', 'content-length': '1147', 'status': '200', 'connection': 'close', 'content-location': 'http://127.0.0.1:8774/v2/40784510a9f046a0a0d70f339f2d71d8/servers?ip6=fd81%3Aaad7%3Afb2%3A0%3Af816%3A3eff%3Afef3%3A8aaa'}
2015-05-01 15:53:56.426 | Body: {"servers": [{"id": "0ab24a98-9725-47cd-86c9-de907da24329", "links": [{"href": "http://127.0.0.1:8774/v2/40784510a9f046a0a0d70f339f2d71d8/servers/0ab24a98-9725-47cd-86c9-de907da24329", "rel": "self"}, {"href": "http://127.0.0.1:8774/40784510a9f046a0a0d70f339f2d71d8/servers/0ab24a98-9725-47cd-86c9-de907da24329", "rel": "bookmark"}], "name": "ListServerFiltersTestJSON-instance-319015482"}, {"id": "3a8bef8f-4f20-4b9f-89b0-905a8f4ba726", "links": [{"href": "http://127.0.0.1:8774/v2/40784510a9f046a0a0d70f339f2d71d8/servers/3a8bef8f-4f20-4b9f-89b0-905a8f4ba726", "rel": "self"}, {"href": "http://127.0.0.1:8774/40784510a9f046a0a0d70f339f2d71d8/servers/3a8bef8f-4f20-4b9f-89b0-905a8f4ba726", "rel": "bookmark"}], "name": "ListServerFiltersTestJSON-instance-313871351"}, {"id": "ce24a53a-f412-4fb5-8da5-c7d0cbdc5fba", "links": [{"href": "http://127.0.0.1:8774/v2/40784510a9f046a0a0d70f339f2d71d8/servers/ce24a53a-f412-4fb5-8da5-c7d0cbdc5fba", "rel": "self"}, {"href": "http://127.0.0.1:8774/40784510a9f046a0a0d70f339f2d71d8/servers/ce24a53a-f412-4fb5-8da5-c7d0cbdc5fba", "rel": "bookmark"}], "name": "ListServerFiltersTestJSON-instance-950662797"}]}