As a fix to http://bugzilla.ecoinformatics.org/show_bug.cgi?id=2748, I'm applying
the patch sent to me from Mike Frenock when he reported this bug.
This patch changes MetaCatServlet.handleUploadAction() by first setting
a boolean flag on whether the file to be uploaded exists already. If it
doesn't exist, the transaction continues, uploading and registering the
data file. In the event of an Exception during the registration, the file
will be deleted, since the file's existence is not recorded in the database.