snapshot project_id attr not always returned

[rochaporto]

Seems the project_id is not always returned as a os-extended-attr in the snapshots query:

{
  "status": "available",
  "display_name": "snapshot for base-jenkins-agent",
  "created_at": "2014-03-27T05:55:15.000000",
  "display_description": "",
  "volume_id": "e3b40183-8752-4b9d-948f-e9e7a0187a38",
  "metadata": {

  },
  "id": "6d123b0a-c226-4509-b30e-429c914fae37",
  "size": 40
},
{
  "status": "available",
  "display_name": "snapshot for snap2",
  "created_at": "2014-04-14T05:28:21.000000",
  "display_description": "",
  "os-extended-snapshot-attributes:progress": "100%",
  "volume_id": "d7f3856d-327c-4c01-82ac-889ddf565780",
  "os-extended-snapshot-attributes:project_id": "94b566de52f9423fab80ceee8c0a4a23",
  "metadata": {

  },
  "id": "8db14c13-ed5b-4e53-9a03-fb7f51d91764",
  "size": 40
},

Need to check why... the query is being done with all_tenants.