This is a followup to the original HADOOP-18546
patch; cherry-picks of that should include this
or follow up with it.
Removes risk of race conditions in assertions
of ITestReadBufferManager on the state of the in-progress
and completed queues by removing assertions brittle
to race conditions in scheduling/network IO
* Waits for all the executor pool shutdown to complete before
making any assertions
* Assertions that there are no in progress reads MUST be
cut as there may be some and they won't be cancelled.
* Assertions that the completed list is without buffers
of a closed stream are brittle because if there was
an in progress stream which completed after stream.close()
then it will end up in the list.
Contributed by Steve Loughran
0a7dfcc332