AKS data-gatherer missing some information

~~Currently the AKS data gatherer collects information about the configuration of an AKS cluster from the Azure API.~~

~~https://docs.microsoft.com/en-us/rest/api/aks/managedclusters/get~~

~~The information returned includes a list of node pools, referred to as agent pools. However it does not give details of each of these pools. This needs to be fetched separately. We should get the configuration of each node pool so we can make the checks performed in the AKS package more comprehensive.~~

~~https://docs.microsoft.com/en-us/rest/api/aks/agentpools/get~~

~~These will both return separate JSON documents, in fact there will be a JSON document for each node pool. We need to work out how this will be handled in Preflight. We could put them all in a list in master JSON document to evaluate with Rego. Alternatively we could make an AKS node pool data gatherer separately, but this would require support for multiple instances of the same data gatherer type to fetch multiple node pools and seems like more work for users.~~

I had misunderstood the problem here. Using the `az aks show --resource-group preflight --name preflight-test-wil` command I can see all the required information, as described in the API spec: https://docs.microsoft.com/en-us/rest/api/aks/managedclusters/get

However when using HTTP GET requests, as the data gatherer does, some information is missing. This also occurs when doing the same thing manually with the `curl` command.

Related to https://github.com/jetstack/preflight/pull/30