Make Tethering#dump asynchronous. am: 5f729e14a3 am: c7a163bae8

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/1678386

Change-Id: Iab29a982cdc237140820f15edc3fe80acaca5683
tree: fa09a59069b17dbf291136bfac8d63369d894527
  1. tests/
  2. Tethering/
  3. .gitignore
  4. OWNERS
  5. PREUPLOAD.cfg
  6. TEST_MAPPING