The invoker pod was cleaned up for some reason and the function call timed out.

apisix calls openwhisk, when the invoker pod is cleaned up for some reason, this will cause apisix to return 503.

POST /api/v1/namespaces/guest/actions/user/getUser?blocking=true&result=true&timeout=8000 HTTP/1.1 499

## Environment details:

* Kubernetes 1.26

## Steps to reproduce the issue:

1. kubectl get po -n openwhisk -owide
2. kubectl delete po -n openwhisk wskowdev-invoker-00-65-guest-getuser
```
# kubectl get po -n openwhisk
NAME READY STATUS RESTARTS AGE
owdev-alarmprovider-67b79fcf46-m7jl8 1/1 Running 0 62d
owdev-apigateway-6fc74d7fcd-4442p 1/1 Running 0 62d
owdev-controller-0 1/1 Running 0 2d23h
owdev-couchdb-84b8749bbf-dcstw 1/1 Running 0 62d
owdev-gen-certs-zcqnh 0/1 Completed 0 62d
owdev-init-couchdb-nfhv7 0/1 Completed 0 62d
owdev-invoker-0 1/1 Running 0 2d22h
owdev-kafka-0 1/1 Running 0 62d
owdev-kafkaprovider-b4ddfd888-bwk66 1/1 Running 0 62d
owdev-nginx-844c58dd89-ghdmp 1/1 Running 0 62d
owdev-redis-57b7889b49-g7pf6 1/1 Running 0 62d
owdev-wskadmin 1/1 Running 0 62d
owdev-zookeeper-0 1/1 Running 0 62d
wskowdev-invoker-00-18-prewarm-go115 1/1 Running 0 2d22h
wskowdev-invoker-00-19-prewarm-go115 1/1 Running 0 2d22h
wskowdev-invoker-00-65-guest-getuser 1/1 Running 0 21s
```
3. Call the function

## Provide the expected results and outputs:

```
Normal return function call results
```

## Provide the actual results and outputs:

```
root@owdev-nginx-844c58dd89-ghdmp:/logs# tail -f *
==> nginx_access.log <==
172.22.17.143 - 23bc46b1-71f6-4ed5-8c54-816aa4f8c502 [09/Sep/2024:06:38:36 +0000] [#tid_806bbecd8407144cde4ba08e42459828] POST /api/v1/namespaces/guest/actions/user/getUser?blocking=true&result=true&timeout=8000 HTTP/1.1 499 0 - lua-resty-http/0.16.1 (Lua) ngx_lua/10025 10.103.10.24:8080
172.22.49.138 - 23bc46b1-71f6-4ed5-8c54-816aa4f8c502 [09/Sep/2024:06:39:08 +0000] [#tid_a349ba08dedc07338ffdcff80153ede4] POST /api/v1/namespaces/guest/actions/user/getUser?blocking=true&timeout=8000&result=true HTTP/1.1 499 0 - lua-resty-http/0.16.1 (Lua) ngx_lua/10025 10.103.10.24:8080

==> nginx_error.log <==
2024/08/26 10:08:56 [error] 31#31: *14464 connect() failed (111: Connection refused) while connecting to upstream, client: 172.22.49.138, server: ~^(?[0-9a-zA-Z-]+)\.$, request: "POST /api/v1/namespaces/guest/actions/user/getUser?blocking=true&timeout=60000&result=true HTTP/1.1", upstream: "http://10.103.10.24:8080/api/v1/namespaces/guest/actions/user/getUser?blocking=true&timeout=60000&result=true", host: "10.103.184.89"
```