Removed so called 'default' control file

- This file is not useful at all, using it can harm the system and causes invalid bugreports
- If a correct control file is available, default control file is not used
- If a correct control file is not available, it's a wrongly built media (or system error) and thus it would be a mistake to continue anyway
- Also reporting that the file hasn't been found and showing the details from log -- customer should not see this, it's more for developers and QA before it gets out
- See gh#yast/yast-installation#86