Description of problem:
Validation can fail on controller with a syntax error.

Issue is possibly caused by accessing attribute without appropriate prior check.

Trace:
------
                        "controller-0": {
                            "_ansible_no_log": false,
                            "action": "set_fact",
                            "failed": true,
                            "msg": "The task includes an option with an undefined variable. The error was: 'dict object' has no attribute 'os_vif_ovs'\n\nThe error appears to be in '/usr/share/ansible/roles/oslo_config_validator/tasks/opt_data_format.yml': line 39, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe offending line appears to be:\n\n\n- name: Building list of replaceable data\n  ^ here\n"
                        }
                    },


Version-Release number of selected component (if applicable):


How reproducible:
Consistently

Steps to Reproduce:
1. Execute `validation run --validation oslo-config-validator` with appropriate inventory
2.
3.

Actual results:
Validation fails ungracefully.

Expected results:
Validation should succeed or gracefully fail.

Additional info:
Can only manifest if the validation execution gets this far.