Enable X-Forward-For logging for Horizon vhost (Apache2)

[Adam Heczko]

Observed on:
Fuel release: "8.0"
  openstack_version: "2015.1.0-8.0"
  api: "1.0"
  build_number: "217"
  build_id: "217"

Problem description:
It was observed that Apache2 Horizon virtual host config doesn't log appropriate IP address.
It logs '%h' rather than '%{X-Forwarded-For}i' which results in logging HAProxy IP address rather than origin initializing HTTP request IP address.

Solution proposal:
Add '%{X-Forwarded-For}i' to Horizon's custom log, or better substitute '%h' with '%{X-Forwarded-For}i'

[Adam Heczko (aheczko-mirantis)]

Apologies for filling bug under wrong project.