OPT: msct_parser: add slash at the end of output_folder
OPT: msct_parser: add slash at the end of output_folder

Former-commit-id: 17946948fb36bb9b902b426fb2796433c7606cff
Former-commit-id: 62fead68d24031154d1db6b2a666b352d844f03d
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox