Optimize 500-backup.inc.php for curlftpfs
Description
This edit is an optimization on the backup script in the case of using curlftpfs to mount an FTP remote directory as the ISPConfig backup path.
Current behaviour
Before this edit, the script store the .sql dump file in the backup directory, then compress it, and remove it. In the suggested use case, this mean the script will output the dump in the remote storage, then retrieve it for compression, then upload the compressed version. This implies extra bandwidth and time to complete the task.
proposed fix
The suggested optimization is to store the dump in the local /tmp directory, then only upload the compressed version.