Fix test failure on Android TV due to built in ethernet interface

Android TV is failing on
EthernetManagerTest.testSetTetheringInterfaceMode_disableEnableEthernet
due to its built in ethernet interface is identified as tethering
interface.
This patch mark the test as only run when no tethering interface
available.

Bug: 389829357
Test: atest EthernetManagerTest
Change-Id: Iab159e224d6baef8ae55ecc2d91a659b90a31538
diff --git a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
index 5b2c9f7..57bc2be 100644
--- a/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
+++ b/tests/cts/net/src/android/net/cts/EthernetManagerTest.kt
@@ -1069,6 +1069,9 @@
 
     @Test
     fun testSetTetheringInterfaceMode_disableEnableEthernet() {
+        // do not run this test if an interface that can be used for tethering already exists.
+        assumeNoInterfaceForTetheringAvailable()
+
         val listener = EthernetStateListener()
         addInterfaceStateListener(listener)