The iso9660 tests test creating isos with different combinations of Joliet, Rock Ridge, and ISO 9660 conformance level. Refactor xorriso argument generation for more readability and extensibility. Signed-off-by: Glenn Washburn <development@efficientek.com> Reviewed-by: Thomas Schmitt <scdbackup@gmx.net> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>