@Override
  public Stack getStack() {
    return stack;
  }
Get whether the specified service is enabled for credential store use.

<pre>
    {@code
      {
        "service_settings" : [
        { "name" : "RANGER",
          "recovery_enabled" : "true",
          "credential_store_enabled" : "true"
        },
        { "name" : "HIVE",
          "recovery_enabled" : "true",
          "credential_store_enabled" : "false"
        },
        { "name" : "TEZ",
          "recovery_enabled" : "false"
        }
      ]
    }
  }
</pre>

@param serviceName - Service name.

@return null if value is not specified; true or false if specified.
ambari-server/src/main/java/org/apache/ambari/server/topology/BlueprintImpl.java