OCS/CNS installation playbook fails with 'glusterfs_heketi_route' is undefined error.

Issue

Installation of OCS/CNS will fail with the following output from the playbook:

TASK [openshift_storage_glusterfs : Generate GlusterFS StorageClass file] *******************************************************************
fatal: [10.10.1.1]: FAILED! => {"changed": false, "failed": true, "msg": "AnsibleUndefinedVariable: 'glusterfs_heketi_route' is undefined"}