CLONE - Backup format is default tgz

Note: This test requires a locally installed Moodle site, in order to be able to edit the config file.

1. Create a backup
2. Download the file and open it with a hex tool
3. Confirm the file starts with #1F8B (gzip file marker)
4. Restore the backup file and make sure it works
5. Add $CFG->usezipbackups = true; to your config.php
6. Create a backup
7. Download the file and open it with a hex tool
8. Confirm the file starts with #504B0304 (zip file marker)
9. Restore the backup file and make sure it works