Add getLegacyVpnInfoPrivileged method

Follows the Google's permission check policy.
Add a getLegacyVpnInfoPrivileged method which skips the permission check
and change getLegacyVpnInfo to check the permission and then call getLegacyVpnInfoPrivileged.
It is already checked in this commit : https://android-review.googlesource.com/#/c/141771/

Signed-off-by: SangJin Cha <sj.cha@lge.com>
Change-Id: I83cfaedbd85745574f3ddf118b11b6e0415483c6

services/core/java/com/android/server/connectivity/Vpn.java

@@ -1009,6 +1009,14 @@ public class Vpn {
     public synchronized LegacyVpnInfo getLegacyVpnInfo() {
         // Check if the caller is authorized.
         enforceControlPermission();
+        return getLegacyVpnInfoPrivileged();
+    }
+
+    /**
+     * Return the information of the current ongoing legacy VPN.
+     * Callers are responsible for checking permissions if needed.
+     */
+    public synchronized LegacyVpnInfo getLegacyVpnInfoPrivileged() {
         if (mLegacyVpnRunner == null) return null;
 
         final LegacyVpnInfo info = new LegacyVpnInfo();