STORM-348: Netty SASL Authentication

Hi Bobby,
  I have made the changes for the SASL Netty Authentication.  Currently the credentials used is with the topology name, but I thought I would be using Kerberos token instead as we agreed I will use randomly generated credentials that are kept in zookeeper.  I will try to find it out which method to call or if you can help me out it would be great.  In the meantime you can review the changes.

 I have tested the changes but didn't create the unit tests.  I will create a separate JIRA for unit test and get it done.  I am learning Clojure and will get it done soon.

Thanks,
Raghavendra Nandagopal
I'm not sure we want to fall back to this on an error.  Because when we try to connect we will end up with NPEs.  Also we don't log the IOException which may make debugging difficult.