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
(cherry picked from commit cbbe7cdd84)

tripleoclient/v1/overcloud_deploy.py

@@ -1368,7 +1368,7 @@ 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,