Remove spurious WTF on pre-U devices.

aosp/2162425 added a WTF if a NetworkAgent changed state before
its native network has been created. This was intended to apply
only to the new U+ codepath, where networks are always created
immediately as soon as their agents register them. But the WTF is
logged on pre-U devices as well.

Fix this so that the WTF is only logged when the new codepath is
running.

Fix: 285999421
Test: TH
Change-Id: I28bda08a006978ab760fe8891bf5cf15b536201a

service/src/com/android/server/ConnectivityService.java

@@ -4480,7 +4480,9 @@ public class ConnectivityService extends IConnectivityManager.Stub
         if (state == NetworkInfo.State.CONNECTED) return true;
         if (state != NetworkInfo.State.CONNECTING) {
             // TODO: throw if no WTFs are observed in the field.
-            Log.wtf(TAG, "Uncreated network in invalid state: " + state);
+            if (shouldCreateNetworksImmediately()) {
+                Log.wtf(TAG, "Uncreated network in invalid state: " + state);
+            }
             return false;
         }
         return nai.isVPN() || shouldCreateNetworksImmediately();