Resolve ambiguous argument.

CTS tests don't have access to TestNetworkAgent and therefore
require overloading this method, which means 'null' is ambiguous.

Bug: 139268426
Test: FrameworksNetTests
Change-Id: I9279718bde30bd98eff901921fb3411d22da72e5
diff --git a/tests/net/java/com/android/server/ConnectivityServiceTest.java b/tests/net/java/com/android/server/ConnectivityServiceTest.java
index c2c3ba3..6ec40df 100644
--- a/tests/net/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/net/java/com/android/server/ConnectivityServiceTest.java
@@ -3729,7 +3729,7 @@
         mCm.requestNetwork(nr, networkCallback, timeoutMs);
 
         // pass timeout and validate that UNAVAILABLE is called
-        networkCallback.expectCallback(CallbackEntry.UNAVAILABLE, null);
+        networkCallback.expectCallback(CallbackEntry.UNAVAILABLE, (Network) null);
 
         // create a network satisfying request - validate that request not triggered
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
@@ -3820,7 +3820,7 @@
             // Simulate the factory releasing the request as unfulfillable and expect onUnavailable!
             testFactory.triggerUnfulfillable(requests.get(newRequestId));
 
-            networkCallback.expectCallback(CallbackEntry.UNAVAILABLE, null);
+            networkCallback.expectCallback(CallbackEntry.UNAVAILABLE, (Network) null);
             testFactory.waitForRequests();
 
             // unregister network callback - a no-op (since already freed by the