Fix notification listener cts test.

Test fails because activity it launches
isn't exported.

Bug: 37656736
Bug: 36657192
Test: cts-tradefed run cts-dev --module DevicePolicyManager --test com.android.cts.devicepolicy.ManagedProfileTest#testCrossProfileNotificationListeners_EmptyWhitelist
Test: cts-tradefed run cts-dev --module DevicePolicyManager --test com.android.cts.devicepolicy.ManagedProfileTest#testCrossProfileNotificationListeners_InWhitelist
Test: cts-tradefed run cts-dev --module DevicePolicyManager --test com.android.cts.devicepolicy.ManagedProfileTest#testCrossProfileNotificationListeners_NullWhitelist
Change-Id: Ida40ff53ffbc2d2065786c114b92acd4536788f2
diff --git a/hostsidetests/devicepolicy/app/NotificationSender/AndroidManifest.xml b/hostsidetests/devicepolicy/app/NotificationSender/AndroidManifest.xml
index d78092b..0f5ac6d 100644
--- a/hostsidetests/devicepolicy/app/NotificationSender/AndroidManifest.xml
+++ b/hostsidetests/devicepolicy/app/NotificationSender/AndroidManifest.xml
@@ -19,7 +19,8 @@
     package="com.android.cts.managedprofiletests.notificationsender">
 
     <application>
-      <activity android:name=".SendNotification" >
+      <activity android:name=".SendNotification"
+                android:exported="true">
       </activity>
     </application>
 </manifest>