small refactorings to test_realizations_per_task
small refactorings to test_realizations_per_task


Former-commit-id: 6687b29418629ce5de7a10fb2da355db915b335d [formerly 6687b29418629ce5de7a10fb2da355db915b335d [formerly 8022337e6ab447f18b44a300bbb75a50e3ed06fc]]
Former-commit-id: 825a853e09f74d6155390be59819b2e1351330a2
Former-commit-id: 1d32e2173a8999e0fddce540ff91ba49c06bb5ff
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine