Closes the current transaction set by writing its footer segment.
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
The CreateTransactionFooter method will write any existing segments to the output stream and then generate and write the transaction set closing segment (SE or UNT). If there are no open transaction sets, an exception will be thrown.