Add haproxy element

This element will be needed for HA deployments. Haproxy will
listen on other-than-default-openstack ports so that
openstack services can be bound to all IP addresses. Keystone
endpoint urls will be updated to point to haproxied non-standard
ports.

Change-Id: Ib8fca60d8e31877aed39739c09a77c68de20f7b0
Merge "Add haproxy element"