Description of problem:
Install OCP with azure_blob as registry beck end storage, according to https://github.com/docker/docker.github.io/blob/master/registry/storage-drivers/azure.md , the parameter "openshift_hosted_registry_storage_azure_blob_realm" should have a default value "core.windows.net" when customer didn't set it.

Version-Release number of the following components:
openshift-ansible-3.7.0-0.125.0.git.0.91043b6.el7

How reproducible:
100%

Steps to Reproduce:
1. Install OCP with azure_blob as registry beck end storage
# cat hosts
...
openshift_hosted_registry_storage_kind=object
openshift_hosted_registry_storage_provider=azure_blob
openshift_hosted_registry_storage_azure_blob_accountname=<hide>
openshift_hosted_registry_storage_azure_blob_accountkey=<hide>
openshift_hosted_registry_storage_azure_blob_container=<hide>
...
2.
3.

Actual results:
# ansible-playbook -i hosts -v /usr/share/ansible/openshift-ansible/playbooks/byo/config.yml
...
TASK [openshift_hosted : Ensure the registry secret exists] ********************
Wednesday 13 September 2017  02:43:12 +0000 (0:00:00.028)       0:13:34.723 *** 
fatal: [master-1.example.com]: FAILED! => {
    "failed": true
}

MSG:

the field 'args' has an invalid value, which appears to include a variable that is undefined. The error was: 'openshift_hosted_registry_storage_azure_blob_realm' is undefined

The error appears to have been in '/usr/share/ansible/openshift-ansible/roles/openshift_hosted/tasks/registry/storage/object_storage.yml': line 5, column 3, but may
be elsewhere in the file depending on the exact syntax problem.

The offending line appears to be:


- name: Ensure the registry secret exists
  ^ here
...

Expected results:
openshift_hosted_registry_storage_azure_blob_realm should set "core.windows.net" as default value.

Additional info: