test: fix failing backup system tests (googleapis#2)

* Remove unnecessary retention period setting

* Fix systests

Author: zoercai

tests/system/test_system.py

@@ -598,22 +598,6 @@ def setUpClass(cls):
         op1.result(30)  # raises on failure / timeout.
         op2.result(30)  # raises on failure / timeout.
 
-        # Add retention period for backups
-        retention_period = "7d"
-        ddl_statements = DDL_STATEMENTS + [
-            "ALTER DATABASE {}"
-            " SET OPTIONS (version_retention_period = '{}')".format(
-                cls.DATABASE_NAME, retention_period
-            )
-        ]
-        db = Config.INSTANCE.database(
-            cls.DATABASE_NAME, pool=pool, ddl_statements=ddl_statements
-        )
-        operation = db.update_ddl(ddl_statements)
-        # We want to make sure the operation completes.
-        operation.result(240)  # raises on failure / timeout.
-        db.reload()
-
         current_config = Config.INSTANCE.configuration_name
         same_config_instance_id = "same-config" + unique_resource_id("-")
         create_time = str(int(time.time()))
@@ -725,7 +709,11 @@ def test_backup_workflow(self):
         database = instance.database(restored_id)
         self.to_drop.append(database)
         operation = database.restore(source=backup)
-        operation.result()
+        restored_db = operation.result()
+        self.assertEqual(version_time, restored_db.restore_info.backup_info.create_time)
+
+        metadata = operation.metadata
+        self.assertEqual(version_time, metadata.backup_info.create_time)
 
         database.drop()
         backup.delete()