Explicitly close RemoteTransfer tempfile

Prevents the Tempfile from staying around until garbage collection on
error.

apps/dashboard/app/models/remote_transfer.rb

@@ -132,6 +132,7 @@ def perform
     errors.add :base, e.message
   ensure
     self.status = OodCore::Job::Status.new(state: :completed)
+    tempfile&.close(true)
   end
 
   def from