Adding test coverage for eth transport overrides am: 2fc1c08cb5 am: ed18ef9f85

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1913619

Change-Id: I2a56ae1d075ed4169610eca0eeb5a7c4329e228d
tree: 8ec1b571d0e18f7a08194d369bc601b3cbb43f13
  1. service-t/
  2. tests/