Fix uploads getting stuck in 'processing' state (fix #3659).

Bug: if an upload timed out while downloading the file, Upload#process!
would catch the error and attempt to retry, but since the upload was
already in the 'processing' state, on the second try `process!` would
bail out immediately and leave the upload stuck in the 'processing' state.

Fix: remove the retry logic from Upload#process!. Let Downloads::File#download!
(which had its own retry logic) handle it instead.

app/logical/downloads/file.rb

@@ -94,7 +94,7 @@ module Downloads
           else
             raise Error.new("HTTP error code: #{res.code} #{res.message}")
           end
-        rescue Errno::ECONNRESET, Errno::ETIMEDOUT, Errno::EIO, Errno::EHOSTUNREACH, Errno::ECONNREFUSED, IOError => x
+        rescue Errno::ECONNRESET, Errno::ETIMEDOUT, Errno::EIO, Errno::EHOSTUNREACH, Errno::ECONNREFUSED, Timeout::Error, IOError => x
           tries += 1
           if tries < 3
             retry