qc.py: add lock on qc report while generating (fixes #2205)
qc.py: add lock on qc report while generating (fixes #2205)


Former-commit-id: 1ca95635aeda382f55ae7e44282897ee41af82ce
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox