Bug 4919: master commit b599471 leaks memory (#364)

Bug 4919: master commit b599471 leaks memory (#364)

Restored the natural order of the following two notifications:
* BodyConsumer::noteMoreBodyDataAvailable() and
* BodyConsumer::noteBodyProductionEnded() or noteBodyProducerAborted().

Commit b599471 unintentionally reordered those two notifications. Client
kids (and possibly other BodyConsumers) relied on the natural order to
end their work. If an HttpStateData job was done with the Squid-to-peer
connection and only waiting for the last adapted body bytes, it would
get stuck and leak many objects. This use case was not tested during
b599471 work.