Added support for changing vault encryption.
    
    The vault-mod command has been modified to support changing vault
    encryption attributes (i.e. type, password, public/private keys)
    in addition to normal attributes (i.e. description). Changing the
    encryption requires retrieving the stored secret with the old
    attributes and rearchiving it with the new attributes.
    
    https://fedorahosted.org/freeipa/ticket/5176
    
    Reviewed-By: Martin Basti <mbasti@redhat.com>