ethernet: temporary mitigation for test that uses TUNSETCARRIER

Since creating an interface without carrier can still have carrier for a
short period of time, the never available assertion is flaky.

This change removes the assertion which is to be readded after
IFF_NO_CARRIER is supported in the kernel.

Test: atest EthernetManagerTest
Bug: 249611919
Change-Id: I437fa2ed34fa28c07b66358b63be40a80d00acf0

tests/cts/net/src/android/net/cts/EthernetManagerTest.kt

@@ -798,7 +798,10 @@ class EthernetManagerTest {
         val iface = createInterface(false /* hasCarrier */)
 
         val cb = requestNetwork(ETH_REQUEST)
-        cb.assertNeverAvailable()
+        // TUNSETCARRIER races with the bring up code, so the network *can* become available despite
+        // it being "created with no carrier".
+        // TODO(b/249611919): re-enable assertion once kernel supports IFF_NO_CARRIER.
+        // cb.assertNeverAvailable()
 
         iface.setCarrierEnabled(true)
         cb.expectAvailable()