[automerger skipped] ethernet: add test for tethered interface callbacks am: bd7a9c2596 -s ours

am skip reason: Merged-In I0bda01265bb8441d1229e63fc957db4e52b15ccb with SHA-1 843cd2cf32 is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/18727987

Change-Id: Ib646e2be561a3dc462f97ff291bf66a1debd0e0b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>