Fix to save externalSignalingServer to user

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/src/main/java/com/nextcloud/talk/jobs/SignalingSettingsWorker.java

@@ -115,6 +115,8 @@ public class SignalingSettingsWorker extends Worker {
                                                                                    .getExternalSignalingTicket());
                         }
 
+                        user.setExternalSignalingServer(externalSignalingServer);
+
                         userManager.saveUser(user).subscribe(new SingleObserver<Integer>() {
                             @Override
                             public void onSubscribe(Disposable d) {