[vsphere] installation errors out when missing topology in a failure domain

    - name: us-east-1
      region: us-east
      zone: us-east-1a
    - name: us-east-2
      region: us-east
      zone: us-east-2a
      topology:
        computeCluster: /IBMCloud/host/vcs-mdcnc-workload-2
        networks:
        - ci-segment-154
        datastore: workload_share_vcsmdcncworkload2_vyC6a

Build from latest master (4.12)

Each time

1. Create install-config.yaml for vsphere multi-zone
2. Leave out a topology section (under failureDomains)
3. Attempt to create cluster

FATAL failed to fetch Terraform Variables: failed to fetch dependency of "Terraform Variables": failed to generate asset "Platform Provisioning Check": platform.vsphere.failureDomains.topology.resourcePool: Invalid value: "//Resources": resource pool '//Resources' not found 

Validation of topology before attempting to create any resources