Implementation of Eth Connect & Disconnect Network am: 9b9952ebe1

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1955448

Change-Id: I58b045be9e06378cca7c35d996f2cc700e5500db
tree: 51e17e5afa62e998e1c079e3d9f77aa0aa126590
  1. service-t/
  2. tests/