Fix BodyPipe/Sink memory leaks associated with auto-consumption (#348)

Fix BodyPipe/Sink memory leaks associated with auto-consumption (#348)

Auto-consumption happens (and could probably leak memory) in many cases,
but this leak was exposed by an eCAP service that blocked or replaced
virgin messages.

The BodySink job termination algorithm relies on body production
notifications. A BodySink job created after the body production had
ended can never stop and, hence, leaks (leaking the associated BodyPipe
object with it). Such a job is also useless:  If production is over,
there is no need to free space for more body data!  This change avoids
creating such leaking and useless jobs.