service: allow creating services without a host to manage them
    
    Add --skip-host-check option to ipa service-add command to allow
    creating services without corresponding host object. This is needed to
    cover use cases where Kerberos services created to handle client
    authentication in a dynamically generated environment like Kubernetes.
    
    Fixes: https://pagure.io/freeipa/issue/7514
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>