Don't show always-on option connecting PPTP vpn

Support for this kind has been taken out so it shouldn't be an option
when connecting (it's already not an option when editing).

Bug: 28807474
Change-Id: Id3e7be390c6813d091e7f897ac82aaf29042beb8
(cherry picked from commit ca75deb7af290745680e8859a0f8da0770802f6e)
diff --git a/src/com/android/settings/vpn2/ConfigDialog.java b/src/com/android/settings/vpn2/ConfigDialog.java
index 92050e9..dd63d13 100644
--- a/src/com/android/settings/vpn2/ConfigDialog.java
+++ b/src/com/android/settings/vpn2/ConfigDialog.java
@@ -316,12 +316,12 @@
     }
 
     private boolean validate(boolean editing) {
-        if (!editing) {
-            return mUsername.getText().length() != 0 && mPassword.getText().length() != 0;
-        }
         if (mAlwaysOnVpn.isChecked() && !getProfile().isValidLockdownProfile()) {
             return false;
         }
+        if (!editing) {
+            return mUsername.getText().length() != 0 && mPassword.getText().length() != 0;
+        }
         if (mName.getText().length() == 0 || mServer.getText().length() == 0 ||
                 !validateAddresses(mDnsServers.getText().toString(), false) ||
                 !validateAddresses(mRoutes.getText().toString(), true)) {