* Attempt to prevent the deadlock in the QueueDiskChannel Test again
This time we're going to adjust the pause tests to only test the right
flag.
* Only switch off pushback once we know that we are not pushing anything else
* Ensure full redirection occurs
* More nicely handle a closed datachan
* And handle similar problems in queue_channel_test
Signed-off-by: Andrew Thornton <art27@cantab.net>