Add TetheringEventCallback CTS test

Test APIs below:
onOffloadStatusChanged(int)

Bug: 153619369
Test: atests CtsTetheringTest
Change-Id: Ia7edd0d3d8184e30373ac8b657299107ff9b4c1e
Merged-In: Ia7edd0d3d8184e30373ac8b657299107ff9b4c1e
(cherry picked from commit c1153b7348dac9d4f0b0ad89acf17e52d00e83b9, aosp/1284554)
1 file changed
tree: 2af16f22be8f3b3c58cff76ef72ac40a1f0dc6b4
  1. tests/