Updating datastore system tests to use project.

Author: dhermes

system_tests/datastore.py

@@ -346,7 +346,7 @@ def test_transaction(self):
     def test_failure_with_contention(self):
         contention_key = 'baz'
         # Fool the Client constructor to avoid creating a new connection.
-        local_client = datastore.Client(dataset_id=CLIENT.dataset_id,
+        local_client = datastore.Client(project=CLIENT.project,
                                         http=object())
         local_client.connection = CLIENT.connection