gateway使用sentinel进行熔断，熔断之后如何获取请求消息体内容？

## Issue Description

Type: *bug report* or *feature request*

### Describe what happened (or what feature you want)
2.2.0版本gateway使用sentinel进行熔断，熔断之后无法获取请求消息体内容
### Describe what you expected to happen
希望可以得到解决方法。谢谢~

### How to reproduce it (as minimally and precisely as possible)

### Tell us your environment

### Anything else we need to know?

No files, tests, entry points, reproduction steps, or environment details are provided. Start by reproducing the request-body loss with the 2.2.0 gateway and Sentinel circuit breaking, then trace the request handling around the circuit-breaker path. Done means a verified way to obtain the request body or a documented limitation and resolution.

Written by the indexing model from the issue text.