Avoiding persistent temp files

[qqmyers]

Working on behalf of TDL, I've found one case for shapefile zips where a successful upload leaves temporary files in the defined temp directory and several ways that user actions to delete or cancel when uploading can cause temp file to remain. I've gone through the code and have changes to submit.

The only cases I'm aware of where 'persistent' temp files can still be created would be 1) where network errors break the communication with the browser and neither a save or cancel is ever received, and 2) some code that writes directly to subdirs under /tmp (eg. some of the R code) which is nominally cleaned up by the operating system.

[pdurbin]

@qqmyers thanks for opening this issue! Perhaps we'll close some of these related issues in favor of this one that you just opened: #2125 #2140 #2848 #3818

[qqmyers]

@pdurbin - this is probably closest to #2140, not sure of the overlap on the others.