CSV Export fails to send prepared File when it's name (without extension) will end with one of this symbols: ".", "c", "s", "v"

Csv export will fail to send prepared file, when it's name (without
extension) will end with one of this symbols: ".", "c", "s", "v". This
happens because rtrim is used to remove file extension and it will also
remove any of extension symbols from end of the filename. Checked other
places in system, where rtrim is used and they are fine.