Create Kerberos Descriptor Database Tables

Create Kerberos Descriptor database tables to store the active Kerberos descriptor data related to a particular cluster and its services.

Kerberos descriptors contain stack/cluster-level details as well as service-level details.

The data needs to be stored such that it may be retrieved to

• generate a single org.apache.ambari.server.state.kerberos.KerberosServiceDescriptor for a particular service in a particular cluster
• generate the entire descriptor hierarchy for a particular cluster into a org.apache.ambari.server.state.kerberos.KerberosDescriptor