Changes to make eth service methods more testable

Updates to make methods in EthernetServiceImpl that rely on
EthernetTracker unit testable. This CL also includes added tests for
such methods in EthernetServiceImplTest.

Bug: 210485380
Test: atest EthernetServiceTests
Change-Id: I63969b60cc4cf9d391e2cd21d02e1bdc8988aba8
4 files changed
tree: 28e16901b342bb8c705e250ea82ada7e687d0dc8
  1. service-t/
  2. tests/