Refactor hazard DB serializer to take advantage of base class code.
Refactor hazard DB serializer to take advantage of base class code.


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Former-commit-id: a29e278b7fefa9065407207a317a9d69eb87f0c5
Former-commit-id: 585ab3464cc9b7c7f26ede344f4bdc70789b1403
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine