Test flaky test: Always wait for handle task to complete

am: e320cdb441

Change-Id: I18fdc1648a3b313c75dc0f2f5a7198e18c56b69d

services/tests/servicestests/src/com/android/server/am/UserControllerTest.java

@@ -484,9 +484,6 @@ public class UserControllerTest {
 
     private void waitForHandlerToComplete(Handler handler, long waitTimeMs)
             throws InterruptedException {
-        if (!handler.hasMessagesOrCallbacks()) { // if nothing queued, do not wait.
-            return;
-        }
         final Object lock = new Object();
         synchronized (lock) {
             handler.post(() -> {