wait-for-broadcast-idle before stopUser in UserLifecycleTests.

Stopping a user heavily depends on broadcast queue, and that gets
crowded after user creation and switches. Which leads to a timeout
on stopping user. This CL makes sure broadcast queue is idle before
stopping a user, to prevent the timeout.

Bug: 200217686
Test: atest MultiUserPerfTests:android.multiuser.UserLifecycleTests --no-bazel-mode
Change-Id: Ic08933212d1e4c8f4966cf1c86b9083b708fcd51

apct-tests/perftests/multiuser/src/android/multiuser/UserLifecycleTests.java

@@ -316,6 +316,8 @@ public class UserLifecycleTests {
                 mIam.startUserInBackground(userId);
             }, Intent.ACTION_USER_STARTED, Intent.ACTION_MEDIA_MOUNTED);
 
+            waitForBroadcastIdle();
+
             mRunner.resumeTiming();
             Log.i(TAG, "Starting timer");
 
@@ -678,6 +680,8 @@ public class UserLifecycleTests {
     }
 
     private void stopUser(int userId, boolean force) throws RemoteException {
+        waitForBroadcastIdle();
+
         final CountDownLatch latch = new CountDownLatch(1);
         mIam.stopUser(userId, force /* force */, new IStopUserCallback.Stub() {
             @Override
@@ -882,4 +886,8 @@ public class UserLifecycleTests {
         assertEquals("", ShellHelper.runShellCommand("setprop " + name + " " + value));
         return oldValue;
     }
+
+    private void waitForBroadcastIdle() {
+        ShellHelper.runShellCommand("am wait-for-broadcast-idle");
+    }
 }