remove Result<> from Blob accessors, add parent (#2608)

* remove Result<> from Blob accessors, add parent
* update chacha's golden
* fixup benches

tests/replicator.rs

@@ -163,7 +163,7 @@ fn test_replicator_startup() {
             if let Ok(blobs) = x {
                 for b in blobs {
                     let br = b.read().unwrap();
-                    assert!(br.index().unwrap() == repair_index);
+                    assert!(br.index() == repair_index);
                     let entry: Entry = deserialize(&br.data()[..br.meta.size]).unwrap();
                     info!("entry: {:?}", entry);
                     assert_ne!(entry.id, Hash::default());