Hadoop credential password storage for the Kafka Storage handler when security is SSL

The Kafka storage handler assumes that if the Hive service is configured with Kerberos then the destination Kafka cluster is also secured with the same Kerberos realm or trust of realms.  The security configuration of the Kafka client can be overwritten due to the additive operations of the Kafka client configs, but, the only way to specify SSL and the keystore/truststore user/pass is via plain text table properties. 

This ticket proposes adding Hadoop credential security to the Kafka storage handler in support of SSL secured Kafka clusters.