Add the Azure subscription-id to the sample delete command given by `inletsctl create`

When you run `inletsctl create`, it prints a command to run in order to delete the server again. The command generated for an Azure deployment is incomplete and will not run without additional parameters.

## Expected Behaviour
* Run the `inletsctl delete` command generated by `inletsctl create`
* The inlets server is deleted.

## Current Behaviour
* The provided command fails:
```
$ inletsctl delete --provider azure --id "inlets-flamboyant-buck2|deployment-c1f95ea9-6957-4aca-be24-26274269e52d"
Using provider: azure
give a value for --access-token-file, --access-token or set the environment variable "INLETS_ACCESS_TOKEN"
```
* Adding --access-token-file with the same file used for create also fails:
```
$ inletsctl delete --provider azure --id "inlets-flamboyant-buck2|deployment-c1f95ea9-6957-4aca-be24-26274269e52d" --access-token-file az-sp.json
Using provider: azure
Deleting host: inlets-flamboyant-buck2|deployment-c1f95ea9-6957-4aca-be24-26274269e52d from azure
resources.GroupsClient#Delete: Failure sending request: StatusCode=400 -- Original Error: Code="InvalidSubscriptionId" Message="The provided subscription identifier 'resourcegroups' is malformed or invalid."
```
* Adding the subscription id succeeds:
```
$ inletsctl delete --provider azure --id "inlets-flamboyant-buck2|deployment-c1f95ea9-6957-4aca-be24-26274269e52d" --access-token-file az-sp.json --subscription-id $SUBSCRIPTION_ID
Using provider: azure
Deleting host: inlets-flamboyant-buck2|deployment-c1f95ea9-6957-4aca-be24-26274269e52d from azure
```

## Possible Solution
Maybe including at least the --subscription-id in the generated command would be a good idea. Alternatively, the subscription ID is already in the access token file so if it's not specified from the command line it could just be read from there too.