Package Pipeline: Run staging up to the "rsync" part with dry-run enabled

[dduportal]

From jenkins-infra/helpdesk#4774 (comment)

Run staging up to the "rsync" part with dry-run enabled: it would allow checking which files are marked as potentially copied to production during promotion.

Note: This change might be tested by setting up a temporarily different destination for promotion, using the file in env/