public static void setData(ZKWatcher zkw, String znode, byte[] data)
    throws KeeperException, KeeperException.NoNodeException {
    setData(zkw, (SetData) ZKUtilOp.setData(znode, data));
  }
Sets the data of the existing znode to be the specified data. The node must exist but no checks
are done on the existing data or version.
<p>
If the node does not exist, a {@link NoNodeException} will be thrown.
<p>
No watches are set but setting data will trigger other watchers of this node.
<p>
If there is another problem, a KeeperException will be thrown.
@param zkw   zk reference
@param znode path of node
@param data  data to set for node
@throws KeeperException if unexpected zookeeper exception
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKUtil.java