Added a Starmap.shutdown [skip hazardlib][demos]
Added a Starmap.shutdown [skip hazardlib][demos]


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Former-commit-id: 8bd8b4a78a73ce3095d87e17250135aaab15b296
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine