Allowing activity occludes keyguard if activity has showWhenLocked flag

Manual testing steps:
- Add showWhenLocked flag to an activity in the manifest
- Start the activity from the managed profile when
  the device is locked
- Verify the activity is shown without having to
  enter the device or work challenge

Bug: 221389857
Test: com.android.server.am.ActivityManagerServiceTest
      Manual testing

Change-Id: I26a3c27b0f8afa3c4b00a35a788f0b2900dde932

services/core/java/com/android/server/wm/ActivityStartInterceptor.java

@@ -358,10 +358,10 @@ class ActivityStartInterceptor {
      * @return The intercepting intent if needed.
      */
     private Intent interceptWithConfirmCredentialsIfNeeded(ActivityInfo aInfo, int userId) {
-        if (!mService.mAmInternal.shouldConfirmCredentials(userId)) {
+        if ((aInfo.flags & ActivityInfo.FLAG_SHOW_WHEN_LOCKED) != 0
+                || !mService.mAmInternal.shouldConfirmCredentials(userId)) {
             return null;
         }
-        // TODO(b/28935539): should allow certain activities to bypass work challenge
         final IntentSender target = createIntentSenderForOriginalIntent(mCallingUid,
                 FLAG_CANCEL_CURRENT | FLAG_ONE_SHOT | FLAG_IMMUTABLE);
         final KeyguardManager km = (KeyguardManager) mServiceContext