Only export overcloud for --stack-only/full deploy

Overcloud export contains stack outputs and passwords.
With ephemeral heat we save the stack outputs and
kill heat. We should export only when stack is created
to generate the configs and not when we run with
--setup-only/--config-download-only.

Also, stop using parsed_args.config_download which is
deprecated.

Change-Id: Ica73e4d04909352646b4518ccd93d01535a243db

tripleoclient/v1/overcloud_deploy.py

@@ -1307,7 +1307,7 @@ class DeployOvercloud(command.Command):
                 self.log.error(e)
 
             try:
-                if parsed_args.config_download:
+                if do_stack:
                     # Create overcloud export
                     data = export.export_overcloud(
                         self.working_dir,