Fix nginx --dry-run (#4889)

* Revert "Don't save keys/csr on dry run (#4380)"

This reverts commit e034b50363.

* Don't save CSRs and keys during dry run

* Factor out _test_obtain_certificate_common

* Add test_obtain_certificate_dry_run

* Wrap key from make_key in util.Key

* Wrap result from make_csr in util.CSR

certbot-nginx/certbot_nginx/tests/util.py

@@ -65,7 +65,6 @@ def get_nginx_configurator(
                     in_progress_dir=os.path.join(backups, "IN_PROGRESS"),
                     server="https://acme-server.org:443/new",
                     tls_sni_01_port=5001,
-                    dry_run=False,
                 ),
                 name="nginx",
                 version=version)