Mahara quickstart templates failing CI with error

Mahara quickstart templates (https://github.com/Azure/azure-quickstart-templates/pull/4657)

### Issue Details

The Travis CI keeps failing mahara-autoscale-cache templates with:

> 1) Template Local Validation mahara-autoscale-cache metadata.json matches schema:
> AssertionError: #:Missing required property "$schema"
> + expected - actual
> -false
> +true
>
> at Context. (test/tests.js:248:15)

All of the JSON templates validate (with a generic JSON linter) and the templates validate using the validate option in the Azure CLI (from my 'test' branch):

> az group deployment validate --resource-group mahara-test --template-file azuredeploy.json --parameters azuredeploy.parameters.json

So I'm not sure what is causing the issue with Travis, any thoughts on the Travis output?

thanks

Start with the mahara-autoscale-cache metadata.json file and the validation failure at test/tests.js:248. Compare the metadata schema expectation with the template, then run the local validation or Travis checks; done means the template passes the metadata schema test and CI no longer reports the missing $schema property.

Written by the indexing model from the issue text.