Memory backend sometimes show empty permissions

[gabisurita]

If you do multiple requests on memory backend, the empty permissions cycle between showing and not showing. The same does not happen with postgres.

gsurita-30820:kinto gsurita$ echo '{"permissions": {"read": []}}' | http put localhost:8888/v1/buckets/b1 -a a:a

{
    "data": {
        "id": "b1",
        "last_modified": 1485553456205
    },
    "permissions": {
        "write": [
            "basicauth:80866b4d0726f35eda20b90bc479a38727c99c68d7c88a87f3b860726a79daeb"
        ]
    }
}

gsurita-30820:kinto gsurita$ echo '{"permissions": {"read": []}}' | http put localhost:8888/v1/buckets/b1 -a a:a

{
    "data": {
        "id": "b1",
        "last_modified": 1485553470501
    },
    "permissions": {
        "collection:create": [],
        "group:create": [],
        "read": [],
        "write": [
            "basicauth:80866b4d0726f35eda20b90bc479a38727c99c68d7c88a87f3b860726a79daeb"
        ]
    }
}

gsurita-30820:kinto gsurita$ echo '{"permissions": {"read": []}}' | http put localhost:8888/v1/buckets/b1 -a a:a

{
    "data": {
        "id": "b1",
        "last_modified": 1485553471419
    },
    "permissions": {
        "write": [
            "basicauth:80866b4d0726f35eda20b90bc479a38727c99c68d7c88a87f3b860726a79daeb"
        ]
    }
}

gsurita-30820:kinto gsurita$ echo '{"permissions": {"read": []}}' | http put localhost:8888/v1/buckets/b1 -a a:a

{
    "data": {
        "id": "b1",
        "last_modified": 1485553472203
    },
    "permissions": {
        "collection:create": [],
        "group:create": [],
        "read": [],
        "write": [
            "basicauth:80866b4d0726f35eda20b90bc479a38727c99c68d7c88a87f3b860726a79daeb"
        ]
    }
}