Moved from SourceForge to Apache.
When a connection to a ZooKeeper server fails, all of the pending requests
will return an error. In reality the requests should be resubmitted when
the client reestablishes a connection to ZooKeeper.
For read requests, it's no big deal to just reissue the request. For update
requests, the ZooKeeper must be able to detect if the request has been
processed and, if so, return the result of the previous execution;
otherwise, it should process the request.