Fix merge conflict.

ag/13210542 was submitted directly into internal and is causing
a merge conflict in NetworkNotificationManagerTest.

Fix the conflict by adding the unused imports.

Test: m
Bug: 175409684
Change-Id: I6eec459a5e5b9900ddeb9e17d90f07432eee1394

tests/net/java/com/android/server/connectivity/NetworkNotificationManagerTest.java

@@ -46,7 +46,9 @@ import androidx.test.runner.AndroidJUnit4;
 import com.android.internal.R;
 import com.android.server.connectivity.NetworkNotificationManager.NotificationType;
 
+import org.junit.AfterClass;
 import org.junit.Before;
+import org.junit.BeforeClass;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.AdditionalAnswers;