Portal download file results on zero length file.

Since the change to using obfuscated filenames when files are stored, the Customer Portal cannot work when portal user tries to download a file...

This line:

https://code.vtiger.com/vtiger/vtigercrm/blob/master/pkg/vtiger/modules/CustomerPortal/modules/CustomerPortal/apis/DownloadFile.php#L66

Only requests the file name and path, not the storedname value.