anyevent: move unlink from http-server to endpoint

anyevent: move unlink from http-server to endpoint

any uploaded file has to be deleted by the corrosponding
endpoint. the file upload was only used by the 'upload to
storage' feature in pve.

this change allows the endpoint to delete the file itself,
making the old and racey`sleep 1` (waiting until the worker
has opened the file) obsolete.

this change breaks all pve-manager versions, in which the
worker does not unlink the temp file itself.

Signed-off-by: Lorenz Stechauner <l.stechauner@proxmox.com>