Description of problem:
Deploy logging and don't set openshift_logging_elasticsearch_kibana_index_mode in inventory, after the playbook finished, check es configmap:
# oc get configmap logging-elasticsearch -o yaml |grep openshift.kibana.index.mode
    openshift.kibana.index.mode: unique
# oc get pod
NAME                                      READY     STATUS    RESTARTS   AGE
logging-curator-1-5q89l                   1/1       Running   0          1m
logging-es-data-master-5mmonrlg-1-hv5pb   2/2       Running   0          1m

then set openshift_logging_elasticsearch_kibana_index_mode=shared_ops in inventory and rerun playbook, the playbook succeed, but the value of openshift.kibana.index.mode didn't change.
# oc get pod
NAME                                      READY     STATUS    RESTARTS   AGE
logging-curator-1-5q89l                   1/1       Running   0          9m
logging-es-data-master-5mmonrlg-2-7stmf   2/2       Running   0          20s
# oc get configmap logging-elasticsearch -o yaml |grep openshift.kibana.index.mode
    openshift.kibana.index.mode: unique
# oc get configmap
NAME                    DATA      AGE
logging-curator         1         24m
logging-elasticsearch   2         25m


Version-Release number of selected component (if applicable):
oc v3.10.12
kubernetes v1.10.0+b81c8f8
features: Basic-Auth GSSAPI Kerberos SPNEGO

Server https://qe-qitang-310-openstackmaster-etcd-1:8443
openshift v3.10.12
kubernetes v1.10.0+b81c8f8

# rpm -qa|grep openshift-ansible
openshift-ansible-roles-3.10.12-1.git.264.fa89aae.el7.noarch
openshift-ansible-docs-3.10.12-1.git.264.fa89aae.el7.noarch
openshift-ansible-playbooks-3.10.12-1.git.264.fa89aae.el7.noarch
openshift-ansible-3.10.12-1.git.264.fa89aae.el7.noarch

logging-elasticsearch-v3.10.12-1

How reproducible:
Always

Steps to Reproduce:
1.Deploy logging, don't set openshift_logging_elasticsearch_kibana_index_mode in inventory
2.wait until all pod are running, check es configmap, openshift.kibana.index.mode: unique
3.set openshift_logging_elasticsearch_kibana_index_mode=shared_ops, and rerun playbook
4.after the playbook finished,check es configmap, openshift.kibana.index.mode is unique, the value hasn't changed

Actual results:
openshift_logging_elasticsearch_kibana_index_mode cann't be changed by inventory variable

Expected results:
openshift_logging_elasticsearch_kibana_index_mode should be the same as inventory variable

Additional info: