This change was triggered by a case where a PuttableProductResolver
was filled by a Worker that produced many products, and one of the
products (A) had a Ref to another product (B), and the product B was
not consumed by any module (it was only accessed through the Ref).
Since the putProduct() released the WaitingTaskList of the Resolver,
that lead to the consumer of A to run, and that consumer dereferenced
the Ref to see that B was not there.

Besides scheduled modules another cases where PuttableProductResolver
is used are Sources inheriting PuttableSourceBase, and TestProcessor.
In these cases the products are put into the Resolvers (or left as
non-produced) before launching the prefetching of the unscheduled
system. Therefore in these use cases the consuming modules do not need
to wait for the Resolver to be filled.

After several fix attempts it seemed easiest to just use the Worker's
WaitingTaskList directly in PuttableProductResolver. This approach
fulfills the requirements of both Worker and Source(-like) use cases,
and even simplifies the code.