(GH-162) Fix azure arc port number

[TraGicCode]

Azure arc listens on port 40342 by default and cannot be changed. This fixes azure arc support which was broken.

Closes #162

[mtanaka2]

Thanks for the quick fix. I reviewed the diff and it correctly addresses the issue I hit — the Arc endpoint URL was defaulting to port 80 because the port was missing, causing "connection refused on 127.0.0.1:80". Adding :40342 (the fixed HIMDS default) resolves it, and I confirmed both call sites (the challenge request and the token request) are updated, with the native IMDS and service-principal paths left untouched. I haven't been able to run it fully end-to-end in my environment yet due to change-control constraints on our AWS compilers, but the code change matches exactly what I diagnosed. Code review LGTM, and I'll follow up with runtime validation once I can schedule the test.