LDAP: Checking the principal should not be considered fatal
    
    The check is too restrictive as the select_principal_from_keytab can
    return something else than user requested right now.
    
    Consider that user query for host/myserver@EXAMPLE.COM, then the
    select_principal_from_keytab function will return "myserver" in primary and
    "EXAMPLE.COM" in realm. So the caller needs to add logic to also break
    down the principal to get rid of the host/ part. The heuristics would
    simply get too complex.
    
    select_principal_from_keytab will error out anyway if there's no
    suitable principal at all.