[Bug]: HTTP client transform fails in case of proxy

### Apache Hop version?

2.6.0

### Java version?

java.version=11.0.9.1

### Operating system

Linux

### What happened?

Using HTTP client transform through an http proxy results in a `"Server Hangup" response (502)`
Disabling preemptive authentication by editing the code and transform works.

### Issue Priority

Priority: 3

### Issue Component

Component: Transforms

Start with the HTTP client transform and reproduce the failure on Apache Hop 2.6.0 with Java 11 on Linux through an HTTP proxy. Compare behavior with preemptive authentication enabled and disabled, and confirm that the completed fix no longer produces the “Server Hangup” 502 response.

Written by the indexing model from the issue text.