ipaserver: deepcopy objectclasses list from IPA config
    
    We need to deepcopy the list of default objectlasses from IPA config
    before assigning it to an entry, in order to avoid further modifications of the
    entry affect the cached IPA config.
    
    Fixes: https://pagure.io/freeipa/issue/9349
    Signed-off-by: Antonio Torres <antorres@redhat.com>
    Reviewed-By: Francisco Trivino <ftrivino@redhat.com>
    Reviewed-By: Thomas Woerner <twoerner@redhat.com>