Fix flaky ConnectivityServiceTest#testNetworkFactoryUnregister

Test: atest ConnectivityServiceTest#testNetworkFactoryUnregister \
      --geneate-new-metrics 100
Bug: 151792032

Change-Id: I1ee7a26186885d3a79a32ec9e45f5bcd656a6680
Merged-In: I1ee7a26186885d3a79a32ec9e45f5bcd656a6680
Merged-In: Iece9e8ad5c51170cd404ac995d0005392d37fe0c
(cherry picked from commit 31c26cdbeb35a6fd6a53a1c25cce6d36b825bf41)

tests/net/java/com/android/server/ConnectivityServiceTest.java

@@ -2464,8 +2464,8 @@ public class ConnectivityServiceTest {
             final MockNetworkFactory testFactory = new MockNetworkFactory(handlerThread.getLooper(),
                     mServiceContext, "testFactory", filter);
             // Register the factory and don't be surprised when the default request arrives.
-            testFactory.register();
             testFactory.expectAddRequestsWithScores(0);
+            testFactory.register();
             testFactory.waitForNetworkRequests(1);
 
             testFactory.setScoreFilter(42);