Add LDAP server fallback to client installer
    
    Change the discovery code to validate all servers, regardless of where
    the originated (either via SRV records or --server). This will prevent
    the client installer from failing if one of those records points to a
    server that is either not running or is not an IPA server.
    
    If a server is not available it is not removed from the list of configured
    servers, simply moved to the end of the list.
    
    If a server is not an IPA server it is removed.
    
    https://fedorahosted.org/freeipa/ticket/3388