risk/job/general: use celery.task.task instead of celery.decorators.task
risk/job/general: use celery.task.task instead of celery.decorators.task

the latter one is deprecated. the difference is in handling "magic
kwargs"


Former-commit-id: 915357b2dd273bddb8a94a6aa1af9877a10463e1 [formerly 19801967b1ba5c6b82b00ef81b893beaa1c53e7c]
Former-commit-id: b8e029a8c19dd55413ac1ce70107c4bcf974213f
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine