Disable always-on VPN in factoryReset

When network setting reset is started while always-on VPN is enabled,
application crash occurs with IllegalStateException in prepareVpn().

Therefore, it's necessary to also disable always-on VPN in factoryReset
before prepareVpn() when turning off VPN.

Bug: 29030858
Change-Id: I08c5406717dd7937d197c2e934a56d037477aafc

services/core/java/com/android/server/ConnectivityService.java

@@ -5206,6 +5206,18 @@ public class ConnectivityService extends IConnectivityManager.Stub
                 }
             }
 
+            // Turn Always-on VPN off
+            if (mLockdownEnabled && userId == UserHandle.USER_SYSTEM) {
+                final long ident = Binder.clearCallingIdentity();
+                try {
+                    mKeyStore.delete(Credentials.LOCKDOWN_VPN);
+                    mLockdownEnabled = false;
+                    setLockdownTracker(null);
+                } finally {
+                    Binder.restoreCallingIdentity(ident);
+                }
+            }
+
             // Turn VPN off
             VpnConfig vpnConfig = getVpnConfig(userId);
             if (vpnConfig != null) {