Sleep in between calls to NoMan service in test

NotificationManagerService has a non-mockable relationship to
System.currentTimeMillis and this test assumes that calls into the
service will not happen in the same millisecond. The fix here is to
sleep for 1ms in between calls to ensure that the clock advances.

Test: atest --rerun-until-failure 100 NotificationManagerServiceTest
Bug: 155331470
Change-Id: Ica6b26a3d72295b0be52c6b1579dde30447ddeaf
diff --git a/services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java b/services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java
index ef4d5db..16aa87b 100755
--- a/services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java
+++ b/services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java
@@ -1339,14 +1339,15 @@
     }
 
     @Test
-    @Ignore
     public void testPostCancelPostNotifiesListeners() throws Exception {
         // WHEN a notification is posted
         final StatusBarNotification sbn = generateNotificationRecord(null).getSbn();
         mBinderService.enqueueNotificationWithTag(PKG, PKG, "tag", sbn.getId(),
                 sbn.getNotification(), sbn.getUserId());
+        Thread.sleep(1);  // make sure the system clock advances before the next step
         // THEN it is canceled
         mBinderService.cancelNotificationWithTag(PKG, PKG, "tag", sbn.getId(), sbn.getUserId());
+        Thread.sleep(1);  // here too
         // THEN it is posted again (before the cancel has a chance to finish)
         mBinderService.enqueueNotificationWithTag(PKG, PKG, "tag", sbn.getId(),
                 sbn.getNotification(), sbn.getUserId());