Bug: not using location of existing resource group on az capi create

[DannyBrito]

When running az capi create with --resource-group=<existing-resource-group. We are not using the location of resource group passed if it exists. As we have extracted the logic to check the existence but not returning location refence to create_workload_cluster

Possible Fix:

We should update behavior of check_resource_group and return resource_group_name and location