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>