Retain media downloads across reentrant progress callbacks

tests/test_media_delivery_download.c

@@ -136,6 +136,8 @@ static struct media_download* make_test_dl(sqlite3* db, struct UTUN_INSTANCE* in
     memcpy(qe->data, dl, sizeof(*dl));
     u_free(dl);
     queue_data_put_with_index(inst->md.downloads, qe);
+    ((struct media_download*)qe->data)->entry = qe;
+    ((struct media_download*)qe->data)->refs = 1;
     return (struct media_download*)qe->data;
 }