Add support for Nullable IpConfiguration am: 9b58f89dc8 am: dc0cb64831 am: 225513e3cb

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

Change-Id: I6fbc0066c4c9e34ad729d242fa353ef3c6a2e2e1
tree: 0aeb15ec0c54163cbe091fa00ec6be365d8e2d54
  1. service-t/
  2. tests/