Fix ActivityLaunchUtils.homeScreenOrBust not dismissing overlay

We run adb shell command to make the device back to home screen,
but it couldn't dismiss system dialog.

broadcasting the intent to dismiss those system dialogs.

Bug: 161581528
Test: atest android.accessibilityservice.cts on TV emulator
Change-Id: Iea25e4d48d86bd36fbe611ed4b4d251facb31e18
diff --git a/tests/accessibilityservice/src/android/accessibilityservice/cts/utils/ActivityLaunchUtils.java b/tests/accessibilityservice/src/android/accessibilityservice/cts/utils/ActivityLaunchUtils.java
index 6885b71..44fd804 100644
--- a/tests/accessibilityservice/src/android/accessibilityservice/cts/utils/ActivityLaunchUtils.java
+++ b/tests/accessibilityservice/src/android/accessibilityservice/cts/utils/ActivityLaunchUtils.java
@@ -61,6 +61,8 @@
     private static final String LOG_TAG = "ActivityLaunchUtils";
     private static final String AM_START_HOME_ACTIVITY_COMMAND =
             "am start -a android.intent.action.MAIN -c android.intent.category.HOME";
+    private static final String AM_BROADCAST_CLOSE_SYSTEM_DIALOG_COMMAND =
+            "am broadcast -a android.intent.action.CLOSE_SYSTEM_DIALOGS";
 
     // Using a static variable so it can be used in lambdas. Not preserving state in it.
     private static Activity mTempActivity;
@@ -134,7 +136,10 @@
         try {
             executeAndWaitOn(
                     uiAutomation,
-                    () -> execShellCommand(uiAutomation, AM_START_HOME_ACTIVITY_COMMAND),
+                    () -> {
+                        execShellCommand(uiAutomation, AM_START_HOME_ACTIVITY_COMMAND);
+                        execShellCommand(uiAutomation, AM_BROADCAST_CLOSE_SYSTEM_DIALOG_COMMAND);
+                    },
                     () -> isHomeScreenShowing(context, uiAutomation),
                     DEFAULT_TIMEOUT_MS,
                     "home screen");