VpnDialogs: prepare for the usages of legacy VPN.

- Use PendingIntent to start activities.
- Handle configs without package names.
- Switch to system UID.

Change-Id: Ia78112a97e3628b603d9e059705e32694ebe142b
diff --git a/packages/VpnDialogs/AndroidManifest.xml b/packages/VpnDialogs/AndroidManifest.xml
index 4e6784c..c0b0a08 100644
--- a/packages/VpnDialogs/AndroidManifest.xml
+++ b/packages/VpnDialogs/AndroidManifest.xml
@@ -1,5 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-        package="com.android.vpndialogs">
+        package="com.android.vpndialogs"
+        android:sharedUserId="android.uid.system">
 
     <application android:label="VpnDialogs">
         <activity android:name=".ConfirmDialog"