Enhancing CAF listener preconfigured check logic to update the preconfigured flag...

Enhancing CAF listener preconfigured check logic to update the preconfigured flag at runtime

1. Preconfigure listener and start listener upon tunnel enabled logic are
   invoked in two different threads.
2. There is a case where preconfigure logic is performed after the
   pre-configured flag is computed in the enable-listener thread.

The current patch invalidates the flag in the start listener thread and
should guarantee the preconfigured status is up-to-date.