TEST: straighten_spinalcord: added integrity testing of curve2straight2curved
TEST: straighten_spinalcord: added integrity testing of curve2straight2curved

Former-commit-id: aeacc6b607d5af8704763c81b58055659eb206f0
Former-commit-id: 6f12570035355a3b55ef6e2ba1087b6e346346d3
3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox