Skip testDefaultNetworkActiveListener on R devices.

testDefaultNetworkActiveListener was flaky on R.
NetworkActivityTracker is not mainlined before S and behavior on R has
difference.
This CL skips the test on R since NetworkActivityTracker behavior on R
is not updatable and updating the test to solve the test flake on R does
not have much benefit.

Bug: 285768880
Test: atest ConnectivityManagerTest
Change-Id: I68c444d587d94b18ed5a58c6d3a05db7b51e2775
diff --git a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
index ee2f6bb..7e7dab7 100644
--- a/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
+++ b/tests/cts/net/src/android/net/cts/ConnectivityManagerTest.java
@@ -3151,7 +3151,8 @@
     }
 
     @AppModeFull(reason = "Need WiFi support to test the default active network")
-    @Test
+    // NetworkActivityTracker is not mainlined before S.
+    @Test @DevSdkIgnoreRule.IgnoreUpTo(Build.VERSION_CODES.R)
     public void testDefaultNetworkActiveListener() throws Exception {
         final boolean supportWifi = mPackageManager.hasSystemFeature(FEATURE_WIFI);
         final boolean supportTelephony = mPackageManager.hasSystemFeature(FEATURE_TELEPHONY);