Remove VPN Overflow menu

- Move always-on option for legacy vpn into the legacy vpn config page
- This implementation doesn't show dialogue when replacing existing always-on vpn
- Continue to disable lockdown option for legacy vpn when "persist.radio.imsregrequired" is true.
  Not applying to vpn app
- Force to save account info when legacy vpn is always-on
- When legacy vpn is always-on, don't try to connect. (Otherwise, an exception is thrown)

TODO: Remove EXTRA_PICK_LOCKDOWN in LockdownVpnTracker in framework

Bug: 26950700
Change-Id: Ia80669359c0b7cdb955c84937156c020ac6e9af5

src/com/android/settings/vpn2/VpnUtils.java

@@ -21,7 +21,9 @@ import android.security.Credentials;
 import android.security.KeyStore;
 
 /**
- * Utility functions for vpn
+ * Utility functions for vpn.
+ *
+ * Keystore methods should only be called in system user
  */
 public class VpnUtils {
 
@@ -35,4 +37,15 @@ public class VpnUtils {
         // Always notify ConnectivityManager after keystore update
         context.getSystemService(ConnectivityManager.class).updateLockdownVpn();
     }
+
+    public static void setLockdownVpn(Context context, String lockdownKey) {
+        KeyStore.getInstance().put(Credentials.LOCKDOWN_VPN, lockdownKey.getBytes(),
+                KeyStore.UID_SELF, /* flags */ 0);
+        // Always notify ConnectivityManager after keystore update
+        context.getSystemService(ConnectivityManager.class).updateLockdownVpn();
+    }
+
+    public static boolean isVpnLockdown(String key) {
+        return key.equals(getLockdownVpn());
+    }
 }