TEST: added test for sct_convert
TEST: added test for sct_convert

Former-commit-id: 9ffee336a4c2f89ba49e239c34a47e80e5ae6074
Former-commit-id: d77415ea50be1824786ff5b8aa0bfb34e57fc5bc
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox