Merge "Optimize neighbor unreachability detection probe fallback." am: 1aecd5e878 am: e0f24af4f5 am: 66d744cf12 am: 7f4df84c22

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

Change-Id: I9b91739cea05de6515580ebbf8c4dfd9c00dea4a