[ranger] update description of Ranger integration related flags
[ranger] update description of Ranger integration related flags

This patch updates the description of Ranger related flags to
make it more clear how to enable Ranger integration.

Change-Id: If782f022ada6606b31d720f1dba793af45e8003e
Reviewed-on: http://gerrit.cloudera.org:8080/15670
Reviewed-by: Andrew Wong <b68e4fdc6430321a6b47400732ff97d7ae91234e@cloudera.com>
Tested-by: Kudu Jenkins

helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu