[LinkTest] Fix speed change (200G->400g) test issue

[Rancho333-CLS]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

The AgentEnsembleSpeedChangeTest.TWOHUNDREDGToFOURHUNDREDG test case in the link test failed.

The root cause is that after the flex port configuration is applied, the variable cablePorts_ is not updated. As a result , FBOSS attempts to access ports that have already been removed, which leads to a crash.

For example, a port is configured in 8x200G mode, with port IDs 1, 2, 3, 4, 5, 6, 7, and 8.
After performing a speed change to switch it to 2x400G mode, only port IDs 1 and 5 remain.
However, since cabledPorts_ is not updated, the system still attempts to check the non-existent ports 2, 3, 4, 6, 7, and 8.

Updating the cabledPorts_ variable after applying the new configuration resolves the issue.

Test Plan

All the pre-commit run checks have passed.

[root github-rancho]# git commit -m "[LinkTest] Fix speed change (200G->400g) test issue"                          
clang-format.............................................................Passed                                   
black................................................(no files to check)Skipped                                   
shellcheck...........................................(no files to check)Skipped
shfmt................................................(no files to check)Skipped                                   
trim trailing whitespace.................................................Passed                                   
fix end of files.........................................................Passed
check yaml...........................................(no files to check)Skipped
check json...........................................(no files to check)Skipped
check for merge conflicts................................................Passed                                   
ruff check...........................................(no files to check)Skipped

After rebuilding the sai_mono_link_test-sai_impl binary, the test result is PASSED.

[       OK ] AgentEnsembleSpeedChangeTest.TWOHUNDREDGToFOURHUNDREDG (99844 ms)
[----------] 1 test from AgentEnsembleSpeedChangeTest (99844 ms total)

[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (99844 ms total)
[  PASSED  ] 1 test.

Please find the complete test log here.

[harshitgulati18]

Thank you for the fix. Which platform is this for?

[Rancho333-CLS]

In theory, this can be reproduced on all platforms, as long as the number of logical ports decreases after a speed change. I discovered and fixed it on IceCube.

[harshitgulati18]

Let's leave a comment above this line that we need to update cabled ports since the previous speed change may add or remove ports

[Rancho333-CLS]

Done

[meta-codesync]

@harshitgulati18 has imported this pull request. If you are a Meta employee, you can view this in D95063445.