Make sure ipapwd_extop takes precedence over passwd_modify_extop
    
    DS core server provides a default plugin (passwd_modify_extop) to handle
    1.3.6.1.4.1.4203.1.11.1 extended op (https://www.ietf.org/rfc/rfc3062.txt)
    
    IPA delivers ipa_pwd_extop plugin that should take precedence over
    the default DS plugin (passwd_modify_extop)
    
    In addition make sure that slapi-nis has a low precedence
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>