libvirt: qemu: enable/disable protected key management ops

libvirt: qemu: enable/disable protected key management ops

Introduces two new -machine option parameters to the QEMU command to
enable/disable the CPACF protected key management operations for a guest:

    aes-key-wrap='on|off'
    dea-key-wrap='on|off'

The QEMU code maps the corresponding domain configuration elements to the
QEMU -machine option parameters to create the QEMU command:

    <cipher name='aes' state='on'>   --> aes-key-wrap=on
    <cipher name='aes' state='off'>  --> aes-key-wrap=off
    <cipher name='dea' state='on'>   --> dea-key-wrap=on
    <cipher name='dea' state='off'>  --> dea-key-wrap=off

Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
Signed-off-by: Daniel Hansel <daniel.hansel@linux.vnet.ibm.com>
Signed-off-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>