The test assume the first tethering upstream would be test network. But
if there are mutiple networks available, this is a wrong assumption
because of race condtion. If tethering choose upstream while wifi or
celluar is available but test network may not available for tethering yet
(it depend on the NetworkCallback from ConnenectivityService), the first
upstream may not be the test network.
Bug: 215224286
Test: atest EthernetTetheringTest
Change-Id: Idfa972008643f1fb5119179383b06e2c8f65c667
95cb089853