Migrate Tethering util functions to CtsTetheringUtils

Bug: 166057846
Bug: 170265597
Test: atest MtsTetheringTest
      atest CtsTetheringTest

Exempt-From-Owner-Approval:
   - this is clean CP from aosp/1460711 which is already approve by owner.
   - owner(Lorenzo) is on the vacation and we need this CL for FRC respin(b/171013290)

Original change: https://android-review.googlesource.com/c/platform/cts/+/1460711

Change-Id: I0f2b116b39eab6fc9f9b201709a7e4146a5c0c5f
Merged-In: I59d529cb50b4b6cdafc6be78ad61a55ee1be0404
(cherry picked from commit b220c5b694ddac3c64f9ba88290a35363413919b)
3 files changed
tree: d0e8c19766caa9708eba631c251c04a196f86bac
  1. tests/