Add quick KVM test pipeline for sonic-mgmt PRs

[devin-ai-integration]

Why I did it

Currently, running KVM tests for sonic-mgmt changes requires a full BuildVS pipeline run (2-4 hours to build the VS image) plus building docker-sonic-mgmt from scratch (2+ hours). This makes iterating on test changes extremely slow. This PR adds a lightweight pipeline that caches the docker-sonic-mgmt image on the self-hosted agent and reuses a pre-built VS image, reducing test turnaround from 5-8 hours to under 2.5 hours (dominated by actual test runtime).

Designed to be attached as a Build Validation policy on the arthur-cog-sonic/sonic-mgmt repo so PRs there automatically trigger KVM tests.

Work item tracking

• Microsoft ADO (number only):

How I did it

Added .azure-pipelines/kvmtest-quick.yml — a single-job pipeline on the sonic-build pool (sonic-build-01) with these stages:

1. Ensure docker-sonic-mgmt image: Checks local Docker cache → falls back to tarball at /data/cache/docker-sonic-mgmt.gz → builds from source only on first run. Persists across pipeline runs on the self-hosted agent.
2. Prepare VS image: Downloads from a user-provided URL or reuses a cached image on the agent.
3. Setup testbed: Spins up the sonic-mgmt container, refreshes the DUT, and deploys minigraph.
4. Run KVM tests: Runs kvmtest.sh for full suites or run_tests.sh for specific scripts.
5. Collect results: Publishes JUnit XML results and KVM dumps on failure.

How to verify it

1. Merge this PR.
2. In ADO (Cisco-SONiC-PoC / SONiC project), create a new pipeline pointing to .azure-pipelines/kvmtest-quick.yml in sonic-buildimage.
3. Queue a manual run with TOPOLOGY=t0 and a VS_IMAGE_URL from a prior successful BuildVS artifact.
4. To enable PR-triggered runs: add this pipeline as a Build Validation policy on the sonic-mgmt repo's master branch.

⚠️ Important: This pipeline has not been end-to-end tested in ADO yet — it requires the agent, a cached VS image, and the sonic-mgmt container infrastructure to be in place.

Human review checklist

• Unused parameter MGMT_IMAGE_SOURCE: Declared (lines ~92-97) with values cache/build but never referenced in any step logic. Should it be wired in, or removed?
• Topology→testbed mapping is duplicated 3 times (testbed setup step, test run step, and the initial case block). A DRY refactor or shared variable would reduce maintenance burden.
• VS image sourcing is manual: The pipeline requires the user to provide VS_IMAGE_URL or pre-stage the image on the agent. Consider adding DownloadPipelineArtifact@2 integration to auto-fetch from the latest BuildVS run.
• Boolean parameter comparison: FORCE_REBUILD_MGMT is type: boolean but compared as string "False" in bash. Verify ADO renders this correctly (likely as True/False capitalized).
• No cleanup step: Successful runs leave Docker containers and KVM VMs on the agent. Should there be a cleanup step?
• Hardcoded paths: /data/sonic-mgmt, /data/sonic-vm, /data/cache assume sonic-build-01's filesystem layout. Acceptable for a self-hosted agent but worth noting.

Which release branch to backport (provide reason below if selected)

• 202305
• 202311
• 202405
• 202411
• 202505
• 202511

N/A — this is a CI/CD infrastructure change, not a feature or bugfix for SONiC itself.

Tested branch (Please provide the tested image version)

Description for the changelog

Add quick KVM test pipeline for sonic-mgmt PR validation with cached docker-sonic-mgmt image.

Link to config_db schema for YANG module changes

N/A

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Link to Devin run: https://cisco-demo.devinenterprise.com/sessions/9e2b276bb37c49cd8b0f54f73dd66118
Requested by: @arthurkkp-cog

[devin-ai-integration]

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