When user restriction turns on, all tethering functions should
be disabled. But tethering functions still work after
restrication is on. Because tethering request would be removed
from mActiveTetheringRequests after starting tethering that
will result in Tethering#isTetheringActive() always returns
false. Thus, update the design to check tethered interface to
ensure that any of tethering function is working.
Bug: 169596583
Test: atest TetheringTests
Test: Manually test that tethering function would be disabled
and notification would show to user after restriction
was on.
Change-Id: Icb9649a5ecdec2d029ac763b5b9b80042ad50eb9
862c8a1ea0