Add support for Nullable IpConfiguration am: 9b58f89dc8 am: dc0cb64831

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/2024300

Change-Id: If9f0241c2d725ea2ecaf405cfe81e02f1a0e4e46
tree: 0aeb15ec0c54163cbe091fa00ec6be365d8e2d54
  1. service-t/
  2. tests/