Elasticsearch: Kibana deployment fails when Windows OS is selected.

[elasticsearch](https://github.com/Azure/azure-quickstart-templates/tree/master/elasticsearch)

### Issue Details
Kibana deployment fails with the following error when Windows OS is selected.

`Unable to process template language expressions for resource '/subscriptions/xxx/resourceGroups/yyy/providers/Microsoft.Compute/virtualMachines/elasticsearch-kibana-vm/extensions/installkibana' at line '166' and column '10'. 'The language expression property 'kibana' doesn't exist, available properties are 'marvel, master, client, data'.`

### Repro steps
1.Deploy with OS = Windows and Kibana = Yes

Start with the Elasticsearch template linked in the issue and reproduce a deployment with Windows OS and Kibana enabled. Inspect the Kibana extension around the reported line and compare the available template properties with the referenced Kibana value; done means the deployment completes successfully without the template-language error.

Written by the indexing model from the issue text.