fix: Update ethernet/multi_iperf3_nic_device job to avoid virtual devices (BugFix)

[ajzobro]

Description

Updated the filter used by the ethernet/multi_iperf3_nic_device... job to avoid attempting to do iperf3 testing of virtual ethernet devices, which are typically used for administration of servers.

As seen in https://certification.canonical.com/certificates/request/2605-17514/

Resolved issues

See above.

Documentation

N/A

Tests

Not tested

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.92%. Comparing base (a9d93d2) to head (ef8c208).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2534   +/-   ##
=======================================
  Coverage   58.92%   58.92%           
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  Files         476      476           
  Lines       48033    48033           
  Branches     8575     8575           
=======================================
  Hits        28305    28305           
+ Misses      18835    18832    -3     
- Partials      893      896    +3     

Flag	Coverage Δ
provider-base	34.10% <ø> (ø)

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[Copilot]

Pull request overview

Updates the Checkbox base provider’s ethernet Multi-NIC iperf3 template selection to skip a known virtual NIC type, reducing false failures when administrative/virtual interfaces are present on server systems.

Changes:

• Narrowed the ethernet/multi_iperf3_nic_device... template resource filter to exclude devices with product_slug == 'Virtual_Ethernet_'.

[rodwsmith]

This looks reasonable on its face, but I would like some checks that this change won't introduce any false positives on the device.product_slug != 'Virtual_Ethernet_' test -- that is, that it won't accidentally exclude something it shouldn't. Maybe write a script to pull down a bunch of submissions (both server and device; say, 100+ submissions of each), check to see if this condition would be met, and then hand-verify that it's all OK?