Add logstash to cacti.

Change-Id: I1635704d92b911446a1450a62c1b733a92e3aeb3
Reviewed-on: https://review.openstack.org/26961
Reviewed-by: Khai Do <zaro0508@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins