install: create ff krb extension on every install, replica install and upgrade
    
    We don't want to copy the extension from master to replica because the
    replica may use newer version of FreeIPA and therefore the extension
    code might be obsolete. Same reason for upgrades.
    
    https://fedorahosted.org/freeipa/ticket/4478
    
    Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>