sct_utils: better temporary directories paths
sct_utils: better temporary directories paths


Former-commit-id: 9ec3a9aca44feb9f2c27acfc85197933f75cd38d
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox