Handle neighbor lost event am: e600bef8f9

Original change: https://android-review.googlesource.com/c/platform/frameworks/opt/net/ethernet/+/1586426

Change-Id: Ic66ac799dfd9287dcd7d5ca6912f6b4a6e07ecad
tree: bdf3d17fdec1457f863bcdfc26d9fa61a49be5ff
  1. service-t/
  2. tests/