Closes the vault.
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:
This method closes the currently-open vault.
For CBDrive, the Force parameter specifies whether to forcefully close any file or directory handles open currently. If Force is false, this method will fail if any handles are currently open. (In CBVault, the Force parameter's value is ignored.)
Note: This method can only be called when Active is true.