Fixed tethering allowed when data disabled

Fixed that tethering clients can continue using
tethering network even after mobile data is disabled.
Fixed by only allowing restricted network request that
has no DUN capability, also tearing down tethering network
when data is disabled (S behavior).

Fix: 241013568
Fix: 240209650
Fix: 241814176
Test: Manual tethering testing with data disabled/enabled +
      atest DataNetworkControllerTest
Change-Id: Ied1f6f0074249720369d1e069aa000ca59e542c8