Take current scheme (HTTP/S) in to account when redirecting.

[paulholden]

See MDL-79361

Failing unit tests relating to curl redirects, because download.moodle.org now redirects everything HTTP -> HTTPS with a 301 response, then the rest redirection script redirects everything back to HTTP:

$ curl -iL "http://download.moodle.org/unittest/test_redir.php?redir=2&verbose=1"
HTTP/1.1 301 Moved Permanently
Date: Tue, 26 Sep 2023 21:41:40 GMT
Transfer-Encoding: chunked
Connection: keep-alive
Cache-Control: max-age=3600
Expires: Tue, 26 Sep 2023 22:41:40 GMT
Location: https://download.moodle.org/unittest/test_redir.php?redir=2&verbose=1
Server: cloudflare
CF-RAY: 80ceac219b0924e4-LHR

HTTP/2 302 
date: Tue, 26 Sep 2023 21:41:40 GMT
content-type: text/html; charset=UTF-8
location: http://download.moodle.org:80/unittest/test_redir.php?redir=1
cf-cache-status: DYNAMIC
server: cloudflare
cf-ray: 80ceac222e90499a-LHR

HTTP/1.1 301 Moved Permanently
Date: Tue, 26 Sep 2023 21:41:40 GMT
Transfer-Encoding: chunked
Connection: keep-alive
Cache-Control: max-age=3600
Expires: Tue, 26 Sep 2023 22:41:40 GMT
Location: https://download.moodle.org/unittest/test_redir.php?redir=1
Server: cloudflare
CF-RAY: 80ceac22bcbd24e4-LHR

HTTP/2 302 
date: Tue, 26 Sep 2023 21:41:40 GMT
content-type: text/html; charset=UTF-8
location: http://download.moodle.org:80/unittest/test_redir.php?done=1
cf-cache-status: DYNAMIC
server: cloudflare
cf-ray: 80ceac22df74499a-LHR

HTTP/1.1 301 Moved Permanently
Date: Tue, 26 Sep 2023 21:41:40 GMT
Transfer-Encoding: chunked
Connection: keep-alive
Cache-Control: max-age=3600
Expires: Tue, 26 Sep 2023 22:41:40 GMT
Location: https://download.moodle.org/unittest/test_redir.php?done=1
Server: cloudflare
CF-RAY: 80ceac231d5a24e4-LHR

HTTP/2 200 
date: Tue, 26 Sep 2023 21:41:41 GMT
content-type: text/html; charset=UTF-8
vary: Accept-Encoding
cf-cache-status: DYNAMIC
server: cloudflare
cf-ray: 80ceac233812499a-LHR

done

So the constant flip/flopping of HTTP/HTTPS breaks assumptions in our tests, e.g. those related to CURLOPT_MAXREDIRS

[jrchamp]

This makes sense to me. Based on how it's currently hosted, I don't expect the http condition to ever be followed, but this is a good minimal change.