iOS setFetchWhenSave 不能获取 pointer 数据

[ycui]

setFetchWhenSave 不能获取 pointer 数据，经确认，安卓是可以的，希望保持一致。

重现代码：

[AVUser logInWithUsernameInBackground:@"cuiyiran" password:@"321" block:^(AVUser *user, NSError *error) {
        AVObject *post = [AVObject objectWithClassName:@"Post"];
        [post setObject:[AVUser currentUser] forKey:@"user"];
        [post setFetchWhenSave:YES];
        [post saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
            NSLog(@"post is %@", post);
        }];
}];