[RFCLAT#9] refactor getinterface_ip() to stop using libnl am: 208b2a1a0c am: 62890f37d3 am: 9b0bb6bde7 am: 518ff057ff

Original change: https://android-review.googlesource.com/c/platform/external/android-clat/+/1908656

Change-Id: I14122a71512eb7ed4489c36d32382e6ce6cde6d4