Stubbed net mgmt API methods in eth service am: 54dcee39e9 am: 9838df1123 am: c0f6096d09

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1923597

Change-Id: I8edb3b9b90f7dc16d033303e19b74f7639548dc6
tree: b640fdbc49cd49632492709dc764a0841e9d8dfb
  1. service-t/
  2. tests/