This should ensure that we apply any special configuration for the
database system (e.g. installing `pgroonga`) before we try to restore
the database contents from the archive.
For pgroonga in particular, this is important so that we can preserve
the configuration of the extension in the `pg_restore` process.
Fixes#12345.
With the S3 file upload backend, we don't store uploads locally, so
the `uploads` directory in the backup will be empty, and more
importantly, LOCAL_UPLOADS_DIR will be None, which the previous code
crashed on.
Fixes permission errors when running restore-backup on a tarball
inaccessible to the zulip user.
Fixes#12125.
Signed-off-by: Anders Kaseorg <anders@zulipchat.com>