convert db test helper methods to static ones
convert db test helper methods to static ones


Former-commit-id: 96427eb92ed8376b08f728635d3fff75076f13fc [formerly 096d3cd12d60749af351e21df77927ee27976406]
Former-commit-id: 34664bf76f4ac546679d5c30b0eb0a1b7ff5b0e4
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine