@Override
            public Object call() throws Exception {
                _connection.exists(path, true);
                return null;
            }
Updates data of an existing znode. The current content of the znode is passed to the {@link DataUpdater} that is
passed into this method, which returns the new content. The new content is only written back to ZooKeeper if
nobody has modified the given znode in between. If a concurrent change has been detected the new data of the
znode is passed to the updater once again until the new contents can be successfully written back to ZooKeeper.

@param <T>
@param path The path of the znode.
@param updater Updater that creates the new contents.
shared/common/src/main/java/com/alibaba/otter/shared/common/utils/zookeeper/ZkClientx.java