FIX: Files are transmitted incorrectly when the SFTP Adapter poll is running at the same time

This issue occurs because the SFTP adapter polls a file before the file is fully written into the polled location. The file is identified and set to zero-length. Because the file is polled, the adapter deletes the file. If an attempt to delete the file is completed before the file is fully written, the delete is retried until it's successful.