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/Android.mk b/packages/VpnDialogs/Android.mk
index 89f010a..ac84125 100644
--- a/packages/VpnDialogs/Android.mk
+++ b/packages/VpnDialogs/Android.mk
@@ -20,6 +20,8 @@
 
 LOCAL_MODULE_TAGS := optional
 
+LOCAL_CERTIFICATE := platform
+
 LOCAL_SRC_FILES := $(call all-java-files-under, src)
 
 LOCAL_PACKAGE_NAME := VpnDialogs