fix: harden Linux E2E scriptless hack and skip it in VHD-build pipelines

[r2k1]

What this PR does / why we need it:

The scriptless E2E "hack" compiles aks-node-controller, uploads it to blob storage, and curls it onto the test node at provision time. It was failing in pipelines. Three fixes:

1. Don't run the hack in pipelines that build the VHD. The Linux PR/release and Windows VHD-build pipelines just built a VHD that already contains the exact binary under test — re-downloading a freshly-compiled copy over the node's outbound path was an unnecessary failure point. The Linux PR builder and Windows template already set DISABLE_SCRIPTLESS_COMPILATION: true; this adds it to the release Linux builder, which was the remaining gap. Standalone E2E pipelines (e2e.yaml, e2e-gpu.yaml, etc.) test published VHDs and intentionally keep the hack to exercise the PR's source.

2. Bump the SAS link expiry 1h → 6h. The signed download link is cached and reused across the whole suite; a 1-hour expiry lapsed mid-run on longer suites.

3. Harden the curl download with --retry-connrefused. Note: deliberately not using --retry-all-errors — it requires curl ≥7.71.0, but the Ubuntu 20.04 FIPS VHDs ship curl 7.68.0 (and run scriptless_nbc subtests via the hack), so that flag would hard-fail provisioning with "unknown option". --retry-connrefused (curl 7.52.0+) is safe on every target VHD.

All changes are confined to e2e/ and pipeline YAML — no product provisioning scripts touched.

Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

This PR hardens the Linux E2E “scriptless” aks-node-controller compilation/download workaround and avoids running it in VHD-build release pipelines where the VHD already contains the binary under test, reducing flaky pipeline failures without touching production provisioning scripts.

Changes:

• Adds --retry-connrefused to curl invocations used to download the hack binary during E2E provisioning.
• Extends the blob SAS/user-delegation credential expiry from 1 hour to 6 hours to prevent mid-suite expiration.
• Sets DISABLE_SCRIPTLESS_COMPILATION: true in the Linux VHD-builder release pipeline E2E stage to skip the compile+download hack.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
e2e/vmss.go	Makes the hack binary download more resilient by retrying connection-refused errors.
e2e/config/azure.go	Extends signed-link expiration to cover longer E2E suites.
.pipelines/.vsts-vhd-builder-release.yaml	Disables scriptless compilation in release VHD-build E2E stage to avoid unnecessary download failures.