• [*] I have searched the issues of this repository and believe that this is not a duplicate.
• [*] I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.6.3
• Operating System version: macos
• Java version: 1.8.0

Steps to reproduce this issue

dubbo2.6.3 服务提供者中使用泛化调用时，绑定attachments时interface错误

dubbo服务提供者中使用泛化调用时，绑定attachments时interface错误，导致thrift encode失败：Could not encode request, the specified interface may be incorrect.

1. 调用方调用 interfaceA.methodA方法
2. methodA中通过泛化调用interfaceB.methodB方法
3. attachements中的interface参数为interfaceA，而不是interfaceB

问题出现在AbstractClusterInvoker中的233行：
`
// binding attachments into invocation.

    Map<String, String> contextAttachments = RpcContext.getContext().getAttachments();

    if (contextAttachments != null && contextAttachments.size() != 0) {

        ((RpcInvocation) invocation).addAttachments(contextAttachments);

    }

`