fix(dra): skip usbip devices in discovery when vhci_hcd has not fully released them

[yaroslavborbat]

Description

During USB device discovery in the DRA plugin, when a USBIP device is detached, there is a race window where the device has already been removed from the USBIP attach info (bus ID set) but is still present in sysfs — because vhci_hcd driver has not fully released it yet.

In this window, the device was incorrectly classified as a regular local USB device and published into the ResourceSlice. It was removed shortly after once vhci_hcd released it, but this caused a brief flap in the ResourceSlice.

The fix detects such devices by resolving the sysfs path symlink and checking whether it goes through the vhci_hcd subsystem. If so, the device is skipped during discovery to prevent the flap.

Why do we need it, and what problem does it solve?

When a USBIP device is detached, there is a brief period during which:

1. The device is no longer in the USBIP attach info (bus ID set).
2. But the sysfs entry still exists because vhci_hcd has not finished cleanup.

As a result, the discovery loop incorrectly published the detaching USBIP device as a local USB device into the ResourceSlice. It was immediately removed on the next reconciliation cycle, but the transient publish caused a flap — unnecessary churn in the ResourceSlice and potentially confusing state for the scheduler.

What is the expected result?

1. Detach a USBIP device from a node while the DRA plugin is running.
2. Observe the ResourceSlice — the detaching USBIP device should NOT appear as a local USB device at any point during the detach process.
3. No flap in the ResourceSlice contents during USBIP device lifecycle events.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vm
type: fix
summary: "Fixed the detection of USB devices on the host: previously, there was a possibility of duplicate USB devices appearing."