Merge branch 'selftests-tc-testing-updates-and-cleanups-for-tdc'

Pedro Tammela says:

====================
selftests: tc-testing: updates and cleanups for tdc

Address the recommendations from the previous series and cleanup some
leftovers.
====================

Link: https://lore.kernel.org/r/20231124154248.315470-1-pctammela@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>