Test fix: Ensuring db cleanup doesn't happen until after test completion...

tests/test_rocksdb_options.rs

@@ -25,6 +25,6 @@ fn test_set_num_levels() {
         let mut opts = Options::default();
         opts.create_if_missing(true);
         opts.set_num_levels(2);
-        let _db = DB::open(&opts, n).unwrap();
+        let _db = DB::open(&opts, &n).unwrap();
     }
 }