Fix User notice in case of suspend to ram for GUEST user

Bug: 148637343
Test: atest CarServiceUnitTest:com.android.car.CarPowerManagementServiceTest
Test: Manual testing : Resuming from S2ram for Guest user should not
      show user notice before user switching to another guest user

Change-Id: Ib16fcd0ad021515316dbd5c6cdedb93e872c0169
(cherry picked from commit 04e3d675fad119eb97a164642c6b74347dc98668)
diff --git a/service/AndroidManifest.xml b/service/AndroidManifest.xml
index e2db410..59ce65d 100644
--- a/service/AndroidManifest.xml
+++ b/service/AndroidManifest.xml
@@ -546,5 +546,11 @@
                 <action android:name="android.intent.action.MAIN" />
             </intent-filter>
         </activity>
+        <activity android:name="com.android.car.am.ContinuousBlankActivity"
+                  android:excludeFromRecents="true"
+                  android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
+                  android:exported="false"
+                  android:launchMode="singleTask">
+        </activity>
     </application>
 </manifest>