Fix data store upload on windows

I was having issues when uploading ShapeFiles to a Geoserver from a Windows client (using the add_data_to_store() method). The problem was twofold: the http.request call would timeout (regardless of the file size) and the unlink() command on the zip file would produce a 'The process cannot access the file' error.

The timeout issue was caused by the fact that the object sent through the http.request call was directly the File object and not the byte stream itself (most likely this was working fine under other OS, but was hanging in Windows).

The second error was caused by the fact that the support.prepare_upload_bundle() method would ignore the File Descriptor object returned, causing a race-condition with the unlink() done within the add_data_to_store() method.

Those two fixes allows me to upload ShapeFiles to a GeoServer without errors.