Add low level helper to get domain level
    
    This can be used only locally on an existing master (uses ldapi).
    Useful to check the domain_level in scripts before the api is
    initialized and/or credentials are available.
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>