Fix bug in testAsyncWriteWithCaching (resolves #1344)
Fix bug in testAsyncWriteWithCaching (resolves #1344)

resolves #1344

The monkey patch to job.fileStore.jobStore.updateFileStream was propagating to
the next job and causing the next job to wait 20s to resolve the promise it was
passed.  Monkey patching job.fileStore.HarbingerFile.read limits the patch to the
scope of the current job and fixes this issue.

BD2KGenomics/slugflow,BD2KGenomics/slugflow