Unstable test due to dictionary keys

[simonff]

In tests/unit/test__datastore_query.py to ensure stable order this code:
entity_pb = mock.Mock(
properties={"a": 0, "b": 1}, spec=("properties",)
)
should be changed to something like:
properties = OrderedDict()
properties['a'] = 0
properties['b'] = 1
entity_pb = mock.Mock(properties=properties, spec=("properties",))