Add haproxy element to overcloud-control image

haproxy element required to be merged before patches
in tripleo-heat-templates

Relies on Ibaadd51e6acd559e008b8aefabfc8df9877a94d7

Change-Id: Iebdce2a1fe452f5a562c0ba63b62251e76955604
Merge "Add haproxy element to overcloud-control image"