crypto: use bytes.Clone

crypto: use bytes.Clone

Change-Id: I92e110023739c6f8f7815c7e47ad7639c4e8812d
Reviewed-on: https://go-review.googlesource.com/c/go/+/435279
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: xie cui <523516579@qq.com>