Description of problem:
The default value of openshift_logging_elasticsearch_proxy_image_prefix is a image name openshift/oauth-proxy.  In general, The image_prefix of Logging/metrics is $registryURL/$namespace rather than $imageName.
For example:
openshift_logging_elasticsearch_image_prefix: "{{ openshift_logging_image_prefix | default(__openshift_logging_image_prefix) }}"
openshift_logging_kibana_image_prefix: "{{ openshift_logging_image_prefix | default(__openshift_logging_image_prefix) }}"
openshift_metrics_image_prefix: "{{ openshift_metrics_image_prefix | default(__openshift_metrics_image_prefix) }}"



Version-Release number of the following components:
openshift-ansible-3.7.0-0.148.0

How reproducible:
always

Steps to Reproduce:
1. grep -r image_prefix /root/openshift-ansible/roles/openshift_logging_elasticsearch/


Actual results:
# grep -r image_prefix /root/openshift-ansible/roles/openshift_logging_elasticsearch/
/root/openshift-ansible/roles/openshift_logging_elasticsearch/defaults/main.yml:openshift_logging_elasticsearch_image_prefix: "{{ openshift_logging_image_prefix | default(__openshift_logging_image_prefix) }}"
/root/openshift-ansible/roles/openshift_logging_elasticsearch/defaults/main.yml:openshift_logging_elasticsearch_proxy_image_prefix: "openshift/oauth-proxy"
/root/openshift-ansible/roles/openshift_logging_elasticsearch/tasks/main.yaml:    image: "{{ openshift_logging_elasticsearch_image_prefix }}logging-elasticsearch:{{ openshift_logging_elasticsearch_image_version }}"
/root/openshift-ansible/roles/openshift_logging_elasticsearch/templates/es.j2:          image: {{openshift_logging_elasticsearch_proxy_image_prefix}}:{{openshift_logging_elasticsearch_proxy_image_version}}

Expected results:

Additional info:
openshift_logging_elasticsearch_proxy_image_prefix should be $registryURL/$namespace