Refactor tether state change callback/broadcast for redactions am: 8a3f2e0460

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3342573

Change-Id: If8ebf99b60fc7617f21ec83a49aeb4a5f0371c0d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>