Do not call SetErrorForJob before the job is done
The code in VolumeDataRequestProcessor::WaitForCompletion would call SetErrorForJob also in the case where it reached the timeout and the job wasn't actually done, and this could lead to at deadlock. It's actually not necessary to set the error here at all, it will also be set in IsCanceled when you try to get the error.
Fixes #197 (closed)