Replace exit by exit 0 at the end of Bash scripts

"exit" returns the current exitcode, not always 0, so this is slightly
different.
I prefer exit 0 as it's not the information used to determine if the
installation went well.
LoL: support installation from local downloader

If the user selects LOCAL installation method but selects the
downloader, the script goes on with DOWNLOAD method using selected file.