Allow to access intermediary request

[speeddragon]

When using gateway-shim@1.0, the accept property cannot be used properly when redirecting.

"gateway-shim-routes": [
  {
    "template": "^/tx$",
    "path": "/~bundler@1.0/tx?codec-device=ans104@1.0&accept=json@1.0"
  },
]

The following example will not convert the response from the headers to JSON format. With this change, the new request is used, and the accept property can be accessed.