From IPA 3.0, services have by default ipakrbprincipal objectclass which
allows ipakrbprincipalalias attribute used for case-insensitive principal
searches. However, services created in previous version do not have
this objectclass (and attribute) and thus case-insensitive searches
may return inconsistent results.
Fill ipakrbprincipalalias on upgrades for all 2.x services. Also treat
Treat the ipakrbprincipal as optional to avoid missing services in
service-find command if the upgrade fails for any reason.
https://fedorahosted.org/freeipa/ticket/3106
