vhost-user: fix memory leak

g_free() was moved from vhost_net_cleanup in commit e6bcb1b, so we should
free net after vhost_net_cleanup

Signed-off-by: linzhecheng <linzhecheng@huawei.com>
Reviewed-by: Marc-André Lureau < marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

net/vhost-user.c

@@ -109,6 +109,7 @@ static int vhost_user_start(int queues, NetClientState *ncs[], CharBackend *be)
 err:
     if (net) {
         vhost_net_cleanup(net);
+        g_free(net);
     }
     vhost_user_stop(i, ncs);
     return -1;