[LocalWebserver] proxy env lowercase

[damianz5]

HTTP_PROXY and HTTPS_PROXY envs should be lowercase.

https://ec.haxx.se/usingcurl/usingcurl-proxies#http_proxy-in-lower-case-only

https://github.com/curl/curl/blob/f762fec323f36fd7da7ad6eddfbbae940ec3229e/docs/libcurl/libcurl-env.3#L37

curl/curl@cb4e2be#diff-58b4cd8fc3c3f6b7a8cd8294d6040174R57

Pull request: #13578

tests:

broken - env is ignored

HTTP_PROXY=http://127.0.0.1:7081 curl 127.0.0.1 -vvv

*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 80 (#0)
> GET / HTTP/1.1
> Host: 127.0.0.1
> User-Agent: curl/7.64.1
> 
< HTTP/1.1 200 OK
...
< 
page response

works:

http_proxy=http://127.0.0.1:7080 curl 127.0.0.1 -vvv

* Uses proxy env variable http_proxy == 'http://127.0.0.1:7080'
*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 7080 (#0)
> GET http://127.0.0.1/ HTTP/1.1
> Host: 127.0.0.1
> User-Agent: curl/7.64.1
> 
< HTTP/1.1 200 OK
...
< 
page response

also works

curl -x http://127.0.0.1:7080 127.0.0.1 -vvv

*   Trying 127.0.0.1...
* TCP_NODELAY set
* Connected to 127.0.0.1 (127.0.0.1) port 7080 (#0)
> GET http://127.0.0.1/ HTTP/1.1
> Host: 127.0.0.1
> User-Agent: curl/7.64.1
> 
< HTTP/1.1 200 OK
...
< 
page response

[javiereguiluz]

Fixed by #13578.