Description of problem:
OAP_PUBLIC_MASTER_URL is not correctly populated in a HA environment.

Version-Release number of the following components:
$ rpm -q openshift-ansible
openshift-ansible-3.5.101-1.git.0.0107544.el7.noarch

$ rpm -q ansible
ansible-2.3.1.0-3.el7.noarch

$ ansible --version
ansible 2.3.1.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = Default w/o overrides
  python version = 2.7.5 (default, May  3 2017, 07:55:04) [GCC 4.8.5 20150623 (Red Hat 4.8.5-14)]

How reproducible:
Every time when running the openshift-logging playbook. It also get reset to the incorrect value when re-running the playbook.

Steps to Reproduce:
1. Set up a HA OCP cluster
2. Run the openshift-logging playbook


Actual results:
Kibana does not redirect to the correct master URL. Which will make logging in impossible since it redirects to the incorrect URL.

Expected results:
The URL that should be populated to this variable should probably be openshift_master_cluster_public_hostname instead of the first master that's being set in the kibana deploymentconfig.

Additional information:
This also goes for OAP_LOGOUT_REDIRECT.
This also happens with kibana-ops deployed.