Validate k8s-cluster-id format in hpecp tenant create

Need to validate the `--k8s-cluster-id` parameter:

```
hpecp tenant create --k8s-cluster-id /api/v2/k8scluster/2 --tenant-type k8s --name test --description long
```

I.e. this should return an error:

```
hpecp tenant create --k8s-cluster-id 2 --tenant-type k8s --name test --description long
```