Return JSON RPC errors for personal_unlockAccount

[nguyer]

The geth JSON RPC client code in the FireFly CLI is wrapped in a retry / delay loop, but the function which unlocks an account wasn't returning errors properly. It would return an error if the HTTP request itself failed (for example if the server wasn't listening) or if the HTTP status code was something other than 200. However, when a JSON RPC server has a problem fulfilling a request, they usually return 200 OK and put the specific JSON RPC error code / message inside the JSON response body. For example:

> POST / HTTP/1.1
> Host: localhost:5100
> User-Agent: curl/7.79.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 168
>
} [168 bytes data]
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< Content-Type: application/json
< Date: Fri, 15 Apr 2022 12:30:36 GMT
< Content-Length: 94
<
{ [94 bytes data]
100   262  100    94  100   168   5541   9904 --:--:-- --:--:-- --:--:-- 26200
* Connection #0 to host localhost left intact
{
  "jsonrpc": "2.0",
  "id": 0,
  "error": {
    "code": -32000,
    "message": "no key for given address or file"
  }
}

This small code change parses JSON RPC errors and returns them, allowing the retry logic to kick in when necessary.

[peterbroadhurst]

👍