Fix MSHV install guest path handling

[pbarbuda]

Description

Installing the Microsoft hypervisor on a guest doesn't work when the host is Windows. The reason is that the path concatenation APIs use Windows path semantics and misinterpret the POSIX paths.

The fix is to use PurePosixPath.

Related Issue

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Documentation update

Checklist

• Description is filled in above
• No credentials, secrets, or internal details are included
• Peer review requested (if not, add required peer reviewers after raising PR)
• Tests executed and results posted below

Test Validation

With this fix, I can run the LISA tests that are part of our automated nightly testing.

Key Test Cases:
verify_mshv_install_succeeds

Impacted LISA Features:
MshvHostInstallSuite

Tested Azure Marketplace Images:
N/A - local Azure Linux Dom0 VHD booted via Hyper-V

Test Results

Image	VM Size	Result
Azure Linux Dom0 VHD, 3.0.20260517, kernel 6.6.121.mshv3-1000.gaf140a66.lv3	Local Hyper-V VM, 2 vCPU / 1 GB	PASSED

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates remote path handling in the MSHV install suite to be OS-agnostic on the controller side by switching from Path to POSIX-only pure paths.

Changes:

• Use PurePosixPath for constant remote file paths (e.g., /home/cloud/..., /boot/efi/...).
• Update _get_file_md5() to accept a PurePath instead of Path.