download_sysext: download first, check later

We need to first download files, and then check its valitidy later.
Otherwise, check_download will simply fail in the beginning, due to
missing files.

src/bin/download_sysext.rs

@@ -262,10 +262,10 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let client = reqwest::Client::new();
 
     for pkg in pkgs_to_dl.iter_mut() {
-        pkg.check_download(&unverified_dir)?;
-
         pkg.download(&unverified_dir, &client).await?;
 
+        pkg.check_download(&unverified_dir)?;
+
         let pkg_unverified = unverified_dir.join(&*pkg.name);
         let pkg_verified = output_dir.join(&*pkg.name);