8a835da certupdate: add commentary about certmonger behaviour

1 file Authored by ftweedal a year ago , Committed by frenaud a year ago ,
    certupdate: add commentary about certmonger behaviour
    
    It is not obvious why we "renew" (reuse only) the IPA CA certificate
    in ipa-certupdate.  Add some commentary to explain this behaviour.
    
    Related: https://pagure.io/freeipa/issue/7751
    See also: https://github.com/freeipa/freeipa/pull/2576#issuecomment-442220840
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>