Filesystem error durring upload of file to session results in file record remaining in session collection.

[scitran]

Filesystem error durring upload of file to session results in file record remaining in session collection.

[gsfr]

@rentzso: Please take this on. I'd suggest that we generally prefer orphaned files over stale database entries. That is, for uploads, place file first, then update database, and for deletes, update database first, then delete file. Actually, with our new hash-based file storage, deletion will need to be handled by a cleanup job. For that, we just need an endpoint; cron functionality will be handled external to the api.

[rentzso]

I have created this pull request to fix this:
#118

The code was handling and cleaning only after IOErrors, but not OSErrors.
Deletes are already done only on the DB, and not on the file system and, as @gsfr was saying, we need the endpoint to do the cleanup.