Fix for GORA-376: Gora Cassandra doesn't accept user credentials for connection

I have documented the issue in JIRA.
https://issues.apache.org/jira/i#browse/GORA-376

As per the advice of "Lewis John McGibbney" I am creating a pull request. Please review the change and accept it if it looks fine.  This is my first pull request for Gora, so please let me know if I haven't followed any guidelines.