MT#59449 sub auth fix possible username without undef domain

* perform_subscriber_auth(): check if domain is undefined
  and use only $user, otherwise $user . @ . $domain.

Change-Id: I3d342fb2c4768c2b7b3e0c08ea41e429b83e9683
(cherry picked from commit 4a9a632da1)

lib/NGCP/Panel/Utils/Auth.pm

@@ -140,7 +140,7 @@ sub perform_subscriber_auth {
         return $res;
     }
 
-    my $userdom = $user . '@' . $domain;
+    my $userdom = $domain ? $user . '@' . $domain : $user;
     return $res if user_is_banned($c, $userdom, 'subscriber');
 
     my $authrs = $c->model('DB')->resultset('provisioning_voip_subscribers')->search({