BUG: msct_register_landmarks: homogenized variable names and fixed input param bug within subfunction
BUG: msct_register_landmarks: homogenized variable names and fixed input param bug within subfunction

Former-commit-id: 9337490abe0d671836b1b04fd28d59f9785abf8d
Former-commit-id: 6ae54f19733ff9273a293f87aa301a47eac06cbe
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox