Remove now-unnecessary sentry_events transition

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>
Always updated Job.updated - and do it first

By updating Job.updated (and more importantly Run.updated) whenever
Job.set_or_update() is called, we can do it at the start of the
transaction. That way we can avoid deadlocking when multiple
transactions updating jobs belonging to the same run are executed
concurrently.

Signed-off-by: Zack Cerza <zack.cerza@inktank.com>