Merge "Optimize neighbor unreachability detection probe fallback." am: 1aecd5e878 am: e0f24af4f5 am: 510d644e8e

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1690573

Change-Id: I31ccd3e9d4cd8e57f041fcd730b6d2c3e011dc8a