Remove all knowledge of tethering from SoftApManager

( dirty cherry-pick from f502d3e20409d81cfefd762b3b44f46dead09a92 )

This logic has moved into Tethering and TetherInterfaceStatemachine,
where it probably always belonged.

Bug: 29054780
Test: WiFi tethering continues to work on angler
      `runtest frameworks-wifi` passes.

Change-Id: Ifff78ea540929fde4abea65716e1f659da2ecfec
3 files changed
tree: 72bf7d15fdf0679f216c04cdefde3ae87727b0af
  1. service/
  2. tests/