Currently, all socket changes are identified using a Network
object. However, the Network object is null for all tethering
interface sockets, which means that the socket cannot be
identified in some places. Therefore, the Network object should
be replaced with a SocketKey object, which includes both the
network and interface index.
Bug: 278018903
Test: atest FrameworksNetTests android.net.cts.NsdManagerTest
Change-Id: Ib49981a4071ecab18c7cf3a8827d1459529492a9
2f236e9ca4