[python] Fix backport of rolling batch non-streaming non-200 error code support

[davidthomas426]

Description

With further testing, we found that pull request #2466 was incomplete. This adds the rest of what was needed.

I ran with this model.py script to cause exceptions to be thrown randomly, as well as a variant that overrides postprocess_results to not set code or error, to ensure that @stop_on_any_exception works as expected.

I also verified that it does not change the behavior unless enabling the feature flag.

model.py:

import djl_python.rolling_batch.lmi_dist_rolling_batch
_update_request_cache_with_output = djl_python.rolling_batch.lmi_dist_rolling_batch.update_request_cache_with_output

_ctr = 0

def update_request_cache_with_output(*args, **kwargs):
    global _ctr
    _ctr += 1
    if _ctr % 20 == 0:
        raise RuntimeError("Uh oh")
    return _update_request_cache_with_output(*args, **kwargs)

djl_python.rolling_batch.lmi_dist_rolling_batch.update_request_cache_with_output = update_request_cache_with_output

import djl_python.huggingface
handle = djl_python.huggingface.handle

$ env | sort | grep SERVING_
SERVING_BACKPORT_FOR_NON_STREAMING_HTTP_ERROR_CODES=true
SERVING_FEATURES=vllm,lmi-dist

$ env | sort | grep OPTION_
OPTION_ENFORCE_EAGER=true
OPTION_MODEL_ID=TheBloke/Llama-2-7B-fp16
OPTION_MPI_MODE=true
OPTION_PIPELINE_PARALLEL_DEGREE=1
OPTION_TENSOR_PARALLEL_DEGREE=4

$ time awscurl -c 1 -N 1 -X POST http://127.0.0.1:8080/invocations --connect-timeout 60 -H Content-type: application/json -v --data {"inputs": "list all the names which start with the letter r","parameters":{"max_new_tokens":10,"seed":2,"do_sample":true}}

WARN Client 0 delay: 0

timestamp: 1729579725060
input: {"inputs": "list all the names which start with the letter r","parameters":{"max_new_tokens":10,"seed":2,"do_sample":true}}
output: > POST //invocations HTTP/1.1
>
> Accept: */*
> User-Agent: awscurl/1.0.0
> Host: 127.0.0.1:8094
> Content-Type: application/json
>
< HTTP/1.1 424 Uh oh
<
< Content-Type: application/json
< x-request-id: c667f402-1df9-4134-92af-923c21071c30
< Pragma: no-cache
< Cache-Control: no-cache; no-store, must-revalidate, private
< Expires: Thu, 01 Jan 1970 00:00:00 UTC
< transfer-encoding: chunked
< connection: keep-alive
<
{"error":"Uh oh","code":424}
real    0m0.539s
user    0m0.812s
sys     0m0.054s