Description of problem:
Deploy logging failed when openshift_logging_storage_kind not set in inventory

Ansible logs:
TASK [openshift_logging_elasticsearch : Set claimRef for NFS PV] ***************
Monday 13 August 2018  02:13:16 +0000 (0:00:00.088)       0:02:01.031 ********* 
fatal: [host-8-251-32.host.centralci.eng.rdu2.redhat.com]: FAILED! => {"msg": "The conditional check 'openshift_logging_storage_kind == \"nfs\"' failed. The error was: error while evaluating conditional (openshift_logging_storage_kind == \"nfs\"): 'openshift_logging_storage_kind' is undefined\n\nThe error appears to have been in '/usr/share/ansible/openshift-ansible/roles/openshift_logging_elasticsearch/tasks/main.yaml': line 403, column 5, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n  - name: Set claimRef for NFS PV\n    ^ here\n"}


Version-Release number of selected component (if applicable):
openshift-ansible-3.11.0-0.14.0.git.0.7bd4429None.noarch

How reproducible:
Always

Steps to Reproduce:
1.Deploy logging using ansible 
2.
3.

Actual results:
Deploy logging failed 

Expected results:


Additional info:
-e parameters:
openshift_logging_install_logging=true
openshift_logging_elasticsearch_memory_limit=2Gi
openshift_logging_elasticsearch_cpu_limit=1000m
openshift_logging_es_nodeselector={"role": "node"}
openshift_logging_es_cluster_size=1
openshift_logging_es_pvc_dynamic=true